JP2006302439A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that bias power, which is different from the bias power which makes an error rate minimum, is determined as the recording power in case that bias power and characteristics of reproduction quality are not ideal due to characteristics of a disk. <P>SOLUTION: When prescribed data are recorded to a plurality of sectors in a prescribed area so as to determine an optimum recording power while sequentially changing recording power, and reproduction signal quality is detected for each kind of recording power, and then an upper and lower limit values of recording power is found based on recording power which makes the reproduction signal quality lower than a preliminarily fixed threshold value of reproduction signal quality; a range of reproduction signal quality, which is higher than the threshold value, is preliminarily determined separately from the threshold value; and recording is made while changing recording power; and when the reproduction signal quality enters in the range at least twice in a reproduction signal quality detecting process, the upper and lower limit values of recording power are determined based on the recording power which makes the reproduction signal quality in the range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus.

  In recent years, optical disc apparatuses are widely used for recording and reproducing video signals and audio signals. Among them, rewritable DVDs such as DVD-RAM, DVD-RW, and DVD + RW have been put on the market, and the market is expanding as a backup medium for computers and a video recording medium replacing a VTR.

  A phase change recording method is adopted in recordable DVD media such as DVD-RAM and DVD-RW. In the phase change recording method, recording is basically performed with information of “0” and “1” corresponding to crystal and amorphous. The recorded “0” and “1” can be detected by irradiating the crystallized portion and the amorphous portion with a laser beam and reproducing the reflected light. In order to make the predetermined position amorphous, the recording layer is heated so that the temperature of the recording layer becomes equal to or higher than the melting point of the recording layer material by irradiating a laser beam with a relatively high peak power. In addition, in order to make a predetermined position into a crystal, it is heated by irradiating a laser beam with a relatively low bias power so that the temperature of the recording layer is near the crystallization temperature below the melting point of the recording layer material. To do. By doing so, the amorphous state and the crystalline state can be reversibly changed.

  When performing overwriting on a normal recordable erasable recordable DVD medium, the recording pulse is modulated between the peak power and the bias laser power lower than that to erase the amorphous mark that has already been recorded. However, since new recording is performed, if information previously recorded in the process of recording new information remains, noise is generated and accurate information cannot be recorded. Also, if the peak power is reduced, marks cannot be formed correctly and recording performance deteriorates. Conversely, if the peak power is too high, stress on the disc increases and repeated recording performance deteriorates. Therefore, in order to perform correct recording, it is essential to set appropriate peak power and bias power.

  An example of the bias power optimization method is as follows. While changing the bias power, trial writing of data and evaluation of the reproduction quality of the data are performed, the characteristics of the reproduction quality with respect to the recording power are measured, and the error rate is measured. There is a method of obtaining bias power values on a low power side and a high power side exceeding a threshold value and setting an optimum bias power based on the two powers (for example, see Patent Document 1 and Non-Patent Document 1).

  FIG. 6 shows a flowchart of an optimum bias power determination method for a conventional optical disc apparatus. In the flowchart of FIG. 6, the upper limit value of the bias power is obtained in steps 101 to 109, step 110 obtains the lower limit value in the same procedure as the upper limit value detection, and in step 110, the optimum value is obtained from the obtained upper limit value and lower limit value. The bias power is determined.

  When the optical pickup moves to the trial writing area for determining the recording power on the optical disc (S101) and the recording power is set (S102), data is recorded in the trial writing area on the optical disc with the recording power, The recorded data is reproduced (S103). By detecting the BER (byte error rate) of the reproduction signal, the reproduction signal quality is detected, and it is determined whether or not the detection result is smaller than a predetermined threshold value ER1 (S104).

  If the reproduction signal quality of the first recording is higher than ER1 (NO in S104), it is determined whether or not the reproduction signal quality has been lower than ER1 by the previous recording (S107), and the reproduction signal quality is ER1. If it is not smaller (NO in S107), a bias power (S108) lower than the initial power is set (S102), recording and reproduction are performed with the set recording power in the same manner as the previous time (S103), and again. It is determined whether the reproduction signal quality is lower than ER1 (S104). In this manner, recording and reproduction are repeated until the bias power is reduced and the reproduction signal quality becomes lower than ER1, and the average of the bias power when the reproduction signal quality becomes lower than ER1 and the bias power immediately before that is obtained. Determine as the upper limit.

  If the reproduction signal quality of the first recording is lower than ER1 (YES in S104), it is determined whether or not the reproduction signal quality has been greater than ER1 by the previous recording (S105), and the reproduction signal quality is ER1. If it is not larger (NO in S105), a bias power (S106) higher than the initial power is set (S102), and recording and reproduction are performed with the set recording power as before (S103), and again. It is determined whether the reproduction signal quality is lower than ER1 (S104). In this way, recording and playback are repeated until the bias power is reduced and the playback signal quality is greater than ER1, and the average of the bias power when the playback signal quality is greater than ER1 and the bias power immediately before that is obtained. Determine as the upper limit.

  The lower limit value of the bias power is determined by the same method as the determination of the upper limit value (S110), and the average of the upper limit value and the lower limit value of the bias power is determined as the optimum bias power (S111).

  However, the above configuration is based on the premise that the characteristics of the bias power and the reproduction quality are ideal as shown in FIG. 2, for example, and the bias power as shown in FIG. In the case of reproduction quality characteristics, there is a problem that a bias power different from the optimum bias power that minimizes the error rate is determined as the optimum value.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an optical disc apparatus capable of obtaining an optimum recording power even when the relationship between recording power and reproduction quality is not ideal.
JP 2001-338422 A DVD Specialties for Rewritable Disc (DVD-RAM) Part1 PHYSICAL SPECIFICATIONS

  The problem to be solved is that the bias power different from the bias power that minimizes the error rate is determined as the recording power when the bias power and reproduction quality characteristics are not ideal due to the characteristics of the disc. It is.

  To improve the optimum recording power determination means with the objective of determining the optimum bias power that minimizes the error rate as the recording power even when the bias power and reproduction quality characteristics are not ideal due to the characteristics of the disc, etc. Realized. That is, the optical disc apparatus of the present invention controls processing power for converting a signal from an optical disc into a reproduction signal, detection means for detecting the signal quality of the reproduction signal converted by the processing means, and recording power. Control means for performing recording, and in order to determine the optimum recording power, the control means records predetermined data in a plurality of sectors in a predetermined area while sequentially changing the recording power, and the detection means When the reproduction signal quality at each recording power is detected and the upper limit value and the lower limit value of the recording power are obtained based on the recording power at which the reproduction signal quality is worse than a predetermined threshold value of the reproduction signal quality, A stage in which a reproduction signal quality range that is better than the threshold value is determined in advance separately from the threshold, recording is performed while the recording power is sequentially changed, and the reproduction signal quality is detected. And a determination means for determining an upper limit value and a lower limit value of the recording power based on the recording power having the reproduction signal quality in the range when the reproduction signal quality enters the range at least twice. Features.

  The optical disk apparatus of the present invention has an advantage that the bias power with the smallest error rate can be determined as the recording power even when the characteristics of the bias power and the reproduction quality are not ideal due to the characteristics of the disk.

(Embodiment 1)
An optical disk device and an embodiment of the present invention will be described below. FIG. 1 shows a block diagram of Embodiment 1 of the present invention. In FIG. 1, 1 is an optical disk, 2 is an optical pickup, 3 is a reproduction signal processing circuit, 4 is reproduction signal quality detection means, 5 is optimum recording power determination means, 6 is power setting means, and 7 is a laser drive circuit. The optical pickup 2 includes a light source that emits light for recording and reproduction, and an objective lens that condenses the light on the optical disc 1, emits a laser beam of recording power to the optical disc, performs recording on the optical disc, In addition, a laser beam having a reproduction power is emitted to the optical disc, a laser reflected light from the optical disc is received, and information recorded on the optical disc is read. The reproduction signal processing circuit 3 performs reproduction signal processing such as amplification, waveform equalization, binarization and the like on the signal from the optical disc to generate a reproduction signal. The reproduction signal quality detection means 4 inputs a reproduction signal and detects the signal quality. The optimum recording power determining means 5 determines the optimum recording power based on the detection result of the reproduction signal quality at a plurality of recording powers. The recording power setting means 6 sets the recording power in the laser drive circuit 7, and the laser drive circuit 7 drives the laser of the optical pickup according to the set recording power.

  Here, the operation for determining the power during recording will be described. In the phase change optical disc apparatus, the power to be determined includes at least peak power and bias power. In this embodiment, a bias power determination method will be described as an example.

  First, the initial value of the bias power is set in the laser drive circuit 7 by the recording power setting means 6. Subsequently, a signal for recording at a predetermined position on the optical disc is sent to the laser drive circuit, and data is recorded on the optical disc by the optical pickup. At this time, the output light of the semiconductor laser, which is a component of the optical pickup, is collected as a light spot on the optical disc, and a recording mark corresponding to the emission waveform is formed on the optical disc. When the recording is finished, the semiconductor laser of the optical pickup emits light with the reproduction power, reproduces the track on which recording was performed earlier, and a signal that changes depending on the presence or absence of the recording mark on the optical disk is input to the reproduction signal processing circuit. . The reproduction signal processing circuit receives reproduction signal processing such as amplification, waveform equalization, binarization, and the like, and inputs the reproduction signal quality detection means. The reproduction signal quality detection means 104 detects a BER (byte error rate) when the recorded signal is reproduced. FIG. 3 shows the relationship between bias power and BER. In the figure, the horizontal axis represents bias power, and the vertical axis represents BER. Generally, the smaller the BER, the more accurate recording is performed. If the relationship between the bias power and the BER is ideal, the relationship is as shown in FIG. 2, but the relationship between the bias power and the BER is also as shown in FIG.

  FIG. 4 is a flowchart showing the operation of the optimum recording power determination means. The optimum recording power determination method in this embodiment will be described with reference to FIG. FIG. 5 shows the threshold value and the recording power when the relationship between the bias power and the BER is not ideal due to the characteristics of the disk, etc., and is determined using the optimum recording power determination method in the present embodiment. It is shown. In the flowchart of FIG. 4, the upper limit value of the bias power is obtained in steps 11 to 22, and the lower limit value of the bias power is obtained in steps 23 and 24 in the same manner as the upper limit value. In step 25, the obtained upper limit value and lower limit value are obtained. The optimum bias power is determined from the value.

  When the optical pickup moves to the trial writing area for determining the recording power on the optical disc (S11) and the recording power is set (S12), data is recorded in the trial writing area on the optical disc with the recording power, The recorded data is reproduced (S13). By detecting the BER (byte error rate) of the reproduction signal, the reproduction signal quality is detected, and it is determined whether or not the detection result is smaller than a predetermined threshold value ER1 (S14).

  If the reproduction signal quality of the first recording is higher than ER1 (NO in S14), it is determined whether or not the reproduction signal quality has been lower than ER1 by the previous recording (S18), and the reproduction signal quality is ER1. If it is not smaller (NO in S18), a bias power (S19) lower than the initial power is set (S12), and recording and reproduction are performed with the set recording power as before (S13), and again. It is determined whether the reproduction signal quality is lower than ER1 (S14). In this way, recording and reproduction are repeated until the bias power is reduced and the reproduction signal quality becomes lower than ER1, and for example, the bias power when the reproduction signal quality becomes lower than ER1 and the bias power immediately before the reproduction power quality. The average is determined as the upper limit.

  If the reproduction signal quality of the first recording is lower than ER1 (YES in S14), it is determined whether or not the reproduction signal quality has been larger than ER1 by the previous recording (S15), and the reproduction signal quality is ER1. If it is not larger (NO in S15), it is determined whether or not the reproduction signal quality is between predetermined thresholds ER2, ER3 (ER2, ER3 <ER1 ER3 <ER2) (S16). ) If the reproduction signal quality is not between ER2 and ER3 (NO in S16), a bias power (S17) higher than the initial power is set (S12), and recording is performed with the set recording power as before. Playback is performed (S13).

  When the relationship between the bias power and the BER is as shown in FIG. 2, recording and reproduction are repeated until the bias power is increased and the reproduction signal quality is greater than ER1, for example, the reproduction signal The average of the bias power when the quality is greater than ER1 and the bias power immediately before it is determined as the upper limit value (S20), and the lower limit value is similarly detected (S24).

  Here, if the relationship between the bias power and the BER is as shown in FIG. 3, the reproduction signal quality is between ER2 and ER3 when the bias power is increased and recording and reproduction are repeated. There is a case. At this time, the reproduction signal quality is lower than ER1 (YES in S14), the reproduction signal quality is not higher than ER1 (NO in S15) by the previous recording, and the reproduction signal quality is ER2 and ER3. (YES in S16), it is determined whether or not the reproduction signal quality has been between ER2 and ER3 before the previous recording (S21), and the reproduction signal quality is between ER2 and ER3. If not (NO in S21), a higher bias power (S22) is set (S12), and recording and reproduction are performed with the set recording power (S13). When the relationship between the bias power and the BER is as shown in FIG. 3, the reproduction signal quality in this recording is again between ER2 and ER3. At this time, the reproduction signal quality is lower than ER1 (YES in S14), the reproduction signal quality is not higher than ER1 (NO in S15) by the previous recording, and the reproduction signal quality is ER2 and ER3. Since the playback signal quality has been between ER2 and ER3 by the previous recording (YES in S21), the relationship between the bias power and the BER is as shown in FIG. The bias power is stopped from increasing further, and the upper limit value of the bias power is set to, for example, the reproduction signal quality becomes ERD (ER2 <ERD <ER3) and is between ER2 and ER3. The first bias power is determined (S23), and the BER threshold value for detecting the lower limit value is changed from normal ER1 to ERD to detect the lower limit value (S25).

  In this manner, the upper limit value and the lower limit value of the bias power are determined. For example, the average of the upper limit value and the lower limit value of the bias power is determined as the optimum bias power (S25). FIG. 5 shows the ER2 and ER3 at this time and the optimum bias power actually determined. Note that ER2 and ER3 may be determined in advance from an example in which the bias power and BER are not ideally related.

  With this series of operations, even when the relationship between the bias power and the BER is not ideal as shown in FIG. 3, the optimum bias power that minimizes the BER can be determined.

  In this embodiment, the average value of the upper limit value and the lower limit value of the bias power is determined as the optimum bias power. However, the lower limit value is taken into account in consideration of the control data value recorded in advance on the disc, the servo state, etc. A value obtained by dividing the upper limit value into, for example, 2: 1 may be set as the optimum power.

  In this embodiment, the reproduction signal quality detection means 4 detects the BER when the recorded signal is reproduced. However, if the reproduction signal quality can be detected other than the BER, the bit error rate, jitter, etc. But you can.

  In this embodiment, the bias power determination method has been described. However, the present invention can naturally be applied to peak power and other recording power.

  In addition, this invention is not limited by the Example described here, The method of obtaining the same effect can be considered elsewhere.

  The optical disc apparatus of the present invention can determine the optimum bias power regardless of the relationship between the bias power and the BER. Therefore, the present invention can further improve the reliability of data recorded on the optical disc.

Block diagram in the embodiment of the present invention The figure which shows an example of the ideal relationship of bias power and BER The figure which shows an example in which bias power and BER are not ideally related Flowchart of optimum bias power determination method in the embodiment of the present invention The figure which shows the threshold value at the time of applying the optimal bias power determination system in embodiment of this invention, and recording power, when bias power and BER are not an ideal relationship A flowchart of a method for determining the optimum bias power of a conventional optical disc apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Optical pick-up 3 Reproduction signal processing circuit 4 Reproduction signal quality detection means 5 Optimal recording power determination means 6 Power setting means 7 Laser drive circuit

Claims (2)

Processing means for converting a signal from the optical disk into a reproduction signal, detection means for detecting the signal quality of the reproduction signal converted by the processing means, and control means for controlling the recording power of the laser recorded on the optical disk; Determining means for determining the recording power of the laser based on the output of the detecting means, and gradually increasing the recording power of the laser by the control means, detecting the reproduction signal quality by the detecting means, and detecting the detection When it is detected that the reproduction signal quality of the detection means is at least twice within a range of a plurality of threshold values of the reproduction signal quality of the means, the determination means performs laser based on the threshold value with the better reproduction signal quality. An optical disc apparatus for determining the recording power of the optical disc. 2. The optical disc apparatus according to claim 1, wherein the detecting means detects an error rate or jitter of a reproduction signal.

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