JP5076846B2 - Optical disk device - Google Patents

Description

  The present invention relates to an optical disc apparatus, and more particularly to tilt control between an optical disc and an optical axis of laser light.

  In the optical disk apparatus, there is a problem that data cannot be recorded and reproduced stably when the optical disk and the optical axis of the laser beam are tilted (tilt state). Therefore, conventionally, a technique has been proposed in which an optical disk apparatus is provided with a tilt sensor to detect the tilt amount and thereby adjust the tilt of the optical pickup.

  FIG. 10 shows a schematic configuration of a conventional optical disc apparatus with a tilt sensor. The optical disk 10 is rotationally driven by a spindle motor 12. The optical pickup 14 is disposed to face the optical disk 10. Laser light from the optical pickup 14 is irradiated and reflected on the optical disk 10 and converted into an electrical signal by a photodetector in the optical pickup 14. A signal from the optical pickup 14 is supplied to the RF signal processing unit 22, and a tracking error signal TE and a focus error signal FE are generated and supplied to the tracking control unit 50 and the focus control unit 52, respectively. The tracking control unit 50 controls the tracking of the optical pickup 14, and the focus control unit 52 controls the focus of the optical pickup 14.

  A tilt sensor 54 is provided facing the optical disk 10 separately from the optical pickup 14, and the tilt amount detected by the tilt sensor 54 is supplied to the tilt drive unit 56. The tilt drive unit 56 adjusts the tilt of the optical pickup 14 so that the tilt amount detected by the tilt sensor 54 becomes zero, and controls the optical axis of the laser beam to be substantially perpendicular to the optical disc 10.

  However, in the configuration in which the tilt sensor 54 is provided separately from the optical pickup 14 to detect the tilt amount, the tilt error signal from the tilt sensor 54 accurately reflects the tilt amount between the optical disc 10 and the optical pickup 14. There is no problem. Further, since the tilt sensor 54 is provided separately, there is a problem that the cost of the entire apparatus is increased.

  On the other hand, a technique for adjusting the tilt amount without providing the tilt sensor 54 is also known. For example, in Patent Document 1 shown below, reflection from a first shift pit formed in advance on an optical disc in a tracking-on state in which the position is controlled on a track using a push-pull signal that is a difference signal of a two-divided photodetector. The light is received by the two-divided photodetector, and the first difference signal which is the difference between the outputs from the first and second light-receiving elements and the reflected light from the second shift pit following the first shift pit are received by the two-divided photodetector. In addition, it is described that the inclination of the recording surface of the optical disc is detected by comparing with a second difference signal which is a difference between outputs from the first and second light receiving elements.

JP 2001-31833 A

  However, in the above prior art, the amount of tilt is detected by comparing the first difference signal and the second difference signal, and depending on the combination of the optical disc and the optical pickup, the tilt between the difference signals due to the influence of signal quality. There is a problem that the amount cannot be detected accurately. For example, when a certain optical pickup is used, there may be a case where it is difficult to accurately evaluate the tilt amount without causing a sufficient difference even if both signals are compared due to the influence of noise of the difference signal itself.

  An object of the present invention is to provide an optical disc apparatus capable of accurately detecting a tilt amount and performing tilt control in any combination of an optical disc and an optical pickup without providing a separate tilt sensor. .

The present invention relates to an optical disk apparatus for recording / reproducing data on / from an optical disk having a first prepit and a second prepit formed so as to be shifted from a track center in a first direction in the track width direction and a second direction opposite thereto. In the land track of the optical disc, the first prepit is formed on the inner peripheral side and the second prepit is formed on the outer peripheral side, and in the groove track, the first prepit is formed on the outer peripheral side, and the second prepit is An error rate detecting means for detecting a first error rate which is a reproduction error rate of the first prepit and a second error rate which is a reproduction error rate of the second prepit, and is formed on the inner peripheral side; Calculating means for calculating a difference between the second error rate and the second error rate, the first error rate and the second error rate. Depending on the bets difference, size of the difference have a tilt controller for adjusting the inclination of the optical axis of the laser beam relative to the optical disc to be equal to or less than a predetermined value, the tilt control means, the sign of the difference The direction in which the inclination of the optical axis of the laser beam is adjusted is determined according to whether the track is the land track or the groove track .

Further, the present invention performs data recording / reproduction with respect to an optical disc having first prepits and second prepits formed so as to be shifted from the track center in the first direction in the track width direction and in the second direction opposite thereto. An optical disc apparatus, wherein an error rate detecting means for detecting a first error rate that is a reproduction error rate of the first prepit and a second error rate that is a reproduction error rate of the second prepit, and the first error rate, Laser light for the optical disc so that the magnitude of the difference is less than or equal to a predetermined value according to the difference between the first error rate and the second error rate, and a calculation means for calculating the difference between the second error rates. When adjusting the tilt of the axis, the laser beam depends on whether the data recording mode is sequential write or random write. And having a tilt control means for changing the adjustment amount for adjusting the inclination of the axis.

Further, the present invention performs data recording / reproduction with respect to an optical disc having first prepits and second prepits formed so as to be shifted from the track center in the first direction in the track width direction and in the second direction opposite thereto. An optical disc apparatus, wherein an error rate detecting means for detecting a first error rate that is a reproduction error rate of the first prepit and a second error rate that is a reproduction error rate of the second prepit, and the first error rate, Laser light for the optical disc so that the magnitude of the difference is less than or equal to a predetermined value according to the difference between the first error rate and the second error rate, and a calculation means for calculating the difference between the second error rates. When adjusting the tilt of the shaft, if the data recording mode is sequential write, the laser is used together with the data recording. Of adjusting the inclination of the optical axis, wherein the recording mode is characterized in that it has a tilt control means for adjusting the inclination of the optical axis of prior the laser beam on the data recording in the case of random write.

  According to the present invention, since the tilt adjustment is performed using the difference between the first error rate and the second error rate, it is possible to accurately detect and control the tilt amount, thereby improving the recording / reproducing characteristics. .

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

  FIG. 1 shows a configuration diagram of an optical disc apparatus according to the present embodiment. The optical disk 10 is rotationally driven by a spindle motor 12 at CAV or CLV. The optical pickup 14 is disposed opposite to the optical disk 10 and records data by irradiating the optical disk 10 with a laser beam with a recording power, and reproduces recorded data by irradiating a laser beam with a reproduction power. At the time of recording, the recording data from the controller 20 is modulated by the encoder 18 and further converted into a driving signal by the LD driving unit 16 to drive the laser diode LD of the optical pickup 14. At the time of reproduction, the return light amount converted into an electric signal by the four-divided photodetector of the optical pickup 14 is supplied to the RF signal processing unit 22, demodulated by the decoder 24, and then supplied to the controller 20 as reproduction data.

  The RF signal processing unit 22 includes an amplifier, an equalizer, a binarization unit, a PLL unit, etc., boosts the RF signal, binarizes it, generates a synchronous clock, and supplies it to the decoder 24. The reproduction RF signal is also supplied to the pre-pit detection unit 26.

  The pre-pit detection unit 26 extracts a pre-pit signal component included in the reproduction RF signal and supplies it to the controller 20 when a pre-pit is formed on the optical disc 10.

  The controller 20 is composed of a microcomputer or the like and supplies recording data to the encoder 18. The encoder 18 modulates the recording data and supplies it to the LD driving unit 16. Further, the controller 20 detects the tilt of the optical axis of the laser beam with respect to the optical disc 10, that is, the tilt amount, based on the pre-pit information. Then, a control signal is supplied to the tilt drive unit 30 in order to search for a position where the tilt becomes smaller according to the detected tilt amount, that is, the optical axis of the laser beam is substantially perpendicular to the recording / reproducing surface of the optical disc 10. To do. The tilt drive unit 30 adjusts the tilt of the optical pickup 14 based on a control signal from the controller 20.

  FIG. 8 shows an example of prepits formed on the optical disc 10. This is the case of DVD-RAM. One sector of the DVD-RAM is composed of a header portion and a data portion, and four address information ID1, ID2, ID3, and ID4 are embossed in the header portion. By reproducing any one of ID1 to ID4, the address information of the sector can be obtained. ID1 and ID2 are formed at the same radial position, and ID3 and ID4 are also formed at the same radial position. ID 1, ID 2 and ID 3, ID 4 are arranged apart from each other in the radial direction of the optical disk 10. That is, ID1 and ID2 are shifted by a predetermined amount in the first direction in the track width direction (radial direction) from the track center to form the first prepit, and ID3 and ID4 are in the second direction (second) in the track width direction from the track center. The second pre-pit is formed by shifting the direction by a predetermined amount in the direction opposite to the first direction. When the laser beam spot 100 from the optical pickup 14 moves rightward in the figure (the optical disk 10 rotates and moves leftward), ID1 and ID2 are detected first, and then ID3 and ID4 are detected. It will be. In the DVD-RAM, data is recorded on lands and grooves to improve recording density. However, when attention is paid to lands, ID1 and ID2 are formed on the inner peripheral side, and ID3 and ID4 are formed on the outer peripheral side. Focusing on the groove, ID1 and ID2 are formed on the outer peripheral side, and ID3 and ID4 are formed on the inner peripheral side. Since the position of the address information is different between the land and the groove, the land and the groove can be distinguished from each other based on such a difference in position. The figure also shows the arrangement of a four-divided photodetector that converts the return light from the optical disk 10 into an electrical signal. The four-divided photodetector is composed of four detectors A to D, and constitutes a photodetector that is divided into two in the radial direction by (A + D) and (B + C). In an on-track state, that is, in a state where the light spot is positioned at the approximate center of the track, ID1 and ID2 are detected at (A + D) and ID3 and ID4 are detected at (B + C). In the groove, ID3 and ID4 are detected at (A + D), and ID1 and ID2 are detected at (B + C).

  FIG. 9 shows a signal of (A + B + C + D) which is the sum of all signals from the four-divided photodetectors A, B, C and D, that is, two signals of the photodetectors (A + D) and (B + C) divided into two in the radial direction. Indicates the sum signal. Since the light spot 100 is detected in the order of ID1, ID2, ID3, and ID4, the ID1 signal, ID2 signal, ID3 signal, and ID4 signal also appear in this order in the sum signal. In the on-track state, the amplitudes of the ID1 signal to ID4 signal are equal. However, when the optical axis of the laser beam is tilted from the vertical direction with respect to the optical disc 10, spot aberration occurs, so that the amplitude of the sum signal differs. For example, when the optical axis of the laser beam is inclined toward the inner peripheral side in the land, the amplitudes of the ID3 signal and the ID4 signal are decreased with respect to the amplitudes of the ID1 signal and the ID2 signal. As the amplitude difference becomes larger, the signal quality on the side where the amplitude becomes relatively smaller deteriorates, so that the address error rate (AER) of the corresponding part deteriorates. For example, when the optical axis of the laser beam inclines toward the inner circumference in the land, the amplitudes of the ID3 signal and the ID4 signal become small, and the AER of ID3 and ID4 deteriorates. It should be noted here that the degree of deterioration of AER due to tilt is significant compared to the amplitude difference due to tilt, and the influence of tilt is that the AER is much larger than the amplitude difference. In other words, AER is a parameter that can be evaluated by expanding the influence of tilt. In this embodiment, paying attention to such a fact, the tilt amount is accurately detected by detecting the AER.

  FIG. 2 shows the address error rate AER of ID1 and ID2 reproduction signals (referred to as ID1 + ID2) and the addresses of ID3 and ID4 reproduction signals (referred to as ID3 + ID4) in the land (LND) and groove (GRV). The tilt angle dependence of the error rate AER is shown. The tilt angle is negative when the optical axis is tilted toward the inner periphery, and is positive when the optical axis is tilted toward the outer periphery. Focusing on the land (LND), when the tilt angle increases in the minus direction, the AER of ID1 + ID2 is substantially constant, whereas the AER of ID3 + ID4 increases rapidly. On the other hand, when the tilt angle increases in the positive direction, the AER of ID1 + ID2 increases rapidly, whereas the AER of ID3 + ID4 increases substantially constant or gently.

  FIG. 3 is a graph showing the relationship between the tilt angle and AER in the case of a land (LND). FIG. 4 is a graph showing the relationship between the tilt angle and AER in the case of the groove (GRV). In FIG. 3, as the tilt angle increases in the negative direction, the AER of ID3 + ID4 increases steeply, while the AER of ID1 + ID2 increases substantially constant or gently. Occurs. When the tilt angle increases in the positive direction, the AER of ID1 + ID2 increases sharply, and a large divergence occurs between the AER of ID1 + ID2 and the AER of ID3 + ID4. Therefore, it is possible to determine whether the tilt angle is positive or negative based on the sign of the difference between the ID1 + ID2 AER and the ID3 + ID4 AER, and to evaluate how much the tilt angle is based on the absolute value of the difference. You can also. For example, in the land track, when the AER of ID1 + ID2 is significantly larger than the AER of ID3 + ID4, specifically, greater than a predetermined determination threshold value, the tilt angle is positive and is evaluated to be, for example, about 0.45 deg. it can. The controller 20 detects the tilt angle by using the change in the sign and absolute value of the difference between the ID1 + ID2 AER and the ID3 + ID4 AER according to the tilt angle, and controls the tilt angle to be almost zero. To do. 3 and 4, the tilt angle is zero when the ID1 + ID2 AER and ID3 + ID4 AER are both zero, or even if they are not completely zero, the ID1 + ID2 AER and ID3 + ID4 AER are substantially equal to or less than a predetermined value. You can see that it means.

  FIG. 5 shows a processing flowchart of the present embodiment. First, the controller 20 detects an address error rate AER of ID1 + ID2 and an address error rate AER of ID3 + ID4, and calculates a difference between them (S101). Then, it is determined whether the magnitude of the difference between the two AERs, that is, whether the absolute value is equal to or less than a predetermined value (S102). If the absolute value of the difference is equal to or smaller than the predetermined value, that is, if there is no substantial difference between the ID1 + ID2 AER and the ID3 + ID4 AER, it is determined that the tilt adjustment has already been completed (S105). Is recorded (S106).

  On the other hand, if the absolute value of the difference exceeds a predetermined value, there is a tilt angle, so the current tilt direction is determined by the sign of the difference (S103). Specifically, the difference is defined as AER of difference = (ID1 + ID2) −AER of (ID3 + ID4). When the track to be recorded is a land track, if the difference> 0, the current tilt angle is plus, If the difference is less than 0, it is determined that the current tilt angle is negative, that is, the inner tilt side is inclined. Of course, if the track to be recorded is a groove, it is determined that the current tilt angle is negative if the difference> 0, and the current tilt angle is positive if the difference <0. Then, the tilt is adjusted according to the current tilt angle determined in S103 and the absolute value of the difference (S104). Specifically, when the tilt angle is positive, the optical axis is tilted in a negative direction by a predetermined amount for correction. When the tilt angle is negative, correction is performed by tilting the optical axis by a predetermined amount in the positive direction. The predetermined amount is determined according to the absolute value of the difference. For example, when the absolute value of the difference is small, the value is small, and when the absolute value of the difference is large, the value is set large. After the tilt adjustment, the AER difference is calculated again (S101), and it is determined whether the absolute value of the difference is equal to or less than a predetermined value (S102). If the absolute value of the difference is equal to or smaller than the predetermined value as a result of the tilt adjustment, the tilt adjustment is finished and data recording is started (S105, S106). Even if the tilt adjustment is performed, the absolute value of the difference still exceeds the predetermined value In this case, the tilt direction is again determined by the sign of the difference and the tilt is readjusted (S104). As described above, the tilt adjustment, the difference calculation, and the comparison between the absolute value of the difference and the predetermined value are repeatedly executed, and are repeatedly executed until the absolute value of the difference becomes equal to or smaller than the predetermined value. At the time of tilt adjustment in S104, if the current tilt angle is positive, the predetermined amount is determined to be negative next, and if the current tilt angle is negative, the predetermined amount is determined to be positive next. You may decide. By repeating the processes of S101 to S104, the absolute value of the difference decreases sequentially, and when the difference value finally becomes equal to or smaller than the predetermined value, the tilt adjustment is finished, and data is recorded at the tilt angle at that time.

  FIG. 6 schematically shows the processing of FIG. First, it is assumed that the tilt angle is θ1. At this time, the AER of ID1 + ID2 is P in the figure, and the AER of ID3 + ID4 is Q in the figure. The difference is ΔAER (1) = P−Q, and the tilt adjustment is performed assuming that the difference ΔAER (1) is larger than a predetermined value. Since the difference ΔAER (1)> 0, the tilt angle is positive. In the tilt adjustment, the tilt angle is adjusted in the negative direction. As a result, the tilt angle changes to θ2. At this time, the AER of ID1 + ID2 is R in the figure, and the AER of ID3 + ID4 is S in the figure. The difference is ΔAER (2) = RS, and the tilt adjustment is completed assuming that the difference ΔAER (2) is smaller than a predetermined value. Although θ2 is not exactly zero, if the error rate is sufficiently low, the recording / reproducing characteristics are not affected.

  As described above, in this embodiment, tilt control is performed using a difference between the address error rate of ID1 + ID2 and the address error rate of ID3 + ID4. The error rate is a parameter that reacts sharply, in other words, sensitively depending on the tilt angle. Therefore, it is possible to accurately evaluate the tilt angle and perform highly accurate and highly stable tilt control.

  In the present embodiment, the case where the tilt control is performed prior to the data recording has been described. However, the tilt adjustment method may be changed according to the data recording mode.

  FIG. 7 shows a flowchart of tilt adjustment in the case of sequential light and random light. This is the process of S104 in FIG. In S102, it is determined that the difference value exceeds a predetermined value, and in S103, the tilt direction is determined by the sign of the difference while considering the land and groove, and then the current recording mode is a sequential write in which addresses to be recorded are continuous. It is determined whether or not (S201). If the address to be recorded is not a sequential write but a random write, the data recording is interrupted (S202), and the tilt adjustment amount is adjusted to a predetermined Δθ1 (S203). This Δθ1 can be set relatively large. On the other hand, when the recording mode is sequential write, the tilt adjustment amount is set to a predetermined Δθ2 and adjusted without interrupting data recording (S204). Here, | Δθ1 |> | Δθ2 |. In the adjustment in S204, the difference value may not necessarily be equal to or smaller than the predetermined value, but the data recording continues. This is because, in the case of sequential writing, it is considered that it is preferable to continuously perform data recording although tilt adjustment is incomplete, rather than interrupting recording to complete tilt adjustment. In the sequential write, the tilt adjustment is gradually performed during the data recording by the process of S204, and the difference value becomes less than or equal to a predetermined value before the tilt adjustment is finished.

  As described above, in the case of sequential write, the tilt adjustment is gradually performed without interrupting the data recording, while in the case of random write, the data is recorded after the tilt adjustment is completed. In addition, the tilt adjustment is performed, and the tilt adjustment is completed prior to the data recording in the random write, so that the optimum tilt adjustment according to the recording mode can be performed.

  In general, since the tilt angle increases toward the outer periphery, the tilt adjustment may be performed from the inner periphery to the intermediate periphery, and the tilt adjustment may be performed from the intermediate periphery to the outer periphery. That is, prior to S101, it may be determined whether or not the radial position where data is to be recorded is from the middle to the outer periphery, and the processing after S101 may be executed only when the position is from the middle to the outer periphery.

  In the present embodiment, the DVD-RAM is exemplified as the optical disk 10, but the present invention is not limited to this, and is formed by shifting from the track center in the first direction in the track width direction and in the second direction opposite thereto. The present invention can be applied to any optical disc having the first prepit and the second prepit.

1 is a block diagram illustrating a configuration of an optical disc device. It is a table | surface figure which shows the relationship between a tilt angle, AER of ID1 + ID2, and AER of ID3 + ID4. It is a graph which shows the relationship between the tilt angle in a land track, AER of ID1 + ID2, and AER of ID3 + ID4. It is a graph which shows the relationship between the tilt angle in a groove track | truck, AER of ID1 + ID2, and AER of ID3 + ID4. It is a processing flowchart of an embodiment. It is explanatory drawing which shows the tilt adjustment process of embodiment. It is a processing flowchart of other embodiments. It is a sector block diagram of DVD-RAM. It is a pre-pit sum signal explanatory drawing. It is a block diagram of the configuration of an optical disc apparatus having a tilt sensor.

Explanation of symbols

  10 optical disc, 12 spindle motor, 14 optical pickup, 16 LD drive unit, 18 encoder, 20 controller, 22 RF signal processing unit, 24 decoder, 26 pre-pit detection unit, 30 tilt drive unit.

Claims (5)

An optical disc apparatus for recording / reproducing data on / from an optical disc having a first prepit and a second prepit formed by shifting from a track center in a first direction in a track width direction and a second direction opposite thereto, In the land track of the optical disc, the first prepit is formed on the inner peripheral side and the second prepit is formed on the outer peripheral side, and in the groove track, the first prepit is formed on the outer peripheral side, and the second prepit is on the inner peripheral side. Formed,
Error rate detection means for detecting a first error rate that is a reproduction error rate of the first prepit and a second error rate that is a reproduction error rate of the second prepit;
Computing means for computing a difference between the first error rate and the second error rate;
Tilt control means for adjusting the tilt of the optical axis of the laser beam with respect to the optical disc so that the magnitude of the difference is a predetermined value or less according to the difference between the first error rate and the second error rate;
I have a,
The optical disc characterized in that the tilt control means determines a direction for adjusting the tilt of the optical axis of the laser light according to the sign of the difference and whether the track is the land track or the groove track. apparatus. The apparatus of claim 1.
The optical disc apparatus characterized in that the tilt control means changes an adjustment amount for adjusting the tilt of the optical axis of the laser light in accordance with the magnitude of the difference . An optical disc apparatus for recording / reproducing data on / from an optical disc having a first prepit and a second prepit formed by shifting from a track center in a first direction in a track width direction and a second direction opposite thereto,
Error rate detection means for detecting a first error rate that is a reproduction error rate of the first prepit and a second error rate that is a reproduction error rate of the second prepit;
Computing means for computing a difference between the first error rate and the second error rate;
When the inclination of the optical axis of the laser beam with respect to the optical disc is adjusted in accordance with the difference between the first error rate and the second error rate so that the magnitude of the difference is a predetermined value or less, the data recording mode is A tilt control means for changing an adjustment amount for adjusting the tilt of the optical axis of the laser light in accordance with a sequential light or a random light;
An optical disc apparatus comprising: The apparatus of claim 3 .
The optical disc apparatus, wherein the tilt control means sets the adjustment amount smaller when the recording mode is sequential write than when random recording is performed . An optical disc apparatus for recording / reproducing data on / from an optical disc having a first prepit and a second prepit formed by shifting from a track center in a first direction in a track width direction and a second direction opposite thereto,
Error rate detection means for detecting a first error rate that is a reproduction error rate of the first prepit and a second error rate that is a reproduction error rate of the second prepit;
Computing means for computing a difference between the first error rate and the second error rate;
When the inclination of the optical axis of the laser beam with respect to the optical disc is adjusted in accordance with the difference between the first error rate and the second error rate so that the magnitude of the difference is a predetermined value or less, the data recording mode is Tilt control means for adjusting the tilt of the optical axis of the laser beam together with data recording in the case of sequential write, and for adjusting the tilt of the optical axis of the laser beam prior to data recording when the recording mode is random write ; ,
An optical disc apparatus comprising:

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