JP4218596B2 - Optical disk device - Google Patents

Description

  The present invention relates to adjustment of the tilt (tilt) of an optical axis of a laser beam with respect to an optical disc of an optical disc apparatus, and more particularly to tilt adjustment when an optical disc having an unrecorded portion is mounted.

  In an optical disk apparatus, it is necessary to precisely control the lens position of the optical pickup for optimum recording and reproduction. Normally, the servo is in the focus direction perpendicular to the disk plane and the tracking direction radial. Control is in progress. However, with the recent increase in the density of optical discs, more precise lens control has been required, and angle control of laser light incident on the disc, so-called tilt control, has also become necessary.

  Here, as tilt control, for example, by arranging a liquid crystal element on the optical path and tilting the optical path, the disc incident angle of the laser beam, that is, the tilt angle is controlled, or an actuator coil different from focus and tracking In general, the tilt angle is controlled by controlling the angle of the lens with respect to the disk using the. The tilt angle is detected by providing a tilt sensor in the optical disk device to detect the tilt amount, or measuring the jitter or error rate of the reproduced RF signal reproduced from the optical disk, and determining the tilt angle at which these values are minimized. Although the optimum tilt angle is used, the former case is disadvantageous in terms of space and cost because a sensor must be provided separately. Therefore, the latter method using jitter and error rate has recently been widely adopted.

  The tilt control based on the jitter and error rate as described above is to detect the tilt angle by reproducing the data signal recorded on the disk, and the data signal is already recorded on the stamper disk or recording area formed in advance by pits. In the case of a recordable disc such as a CD-R or CD-RW in which data has been recorded, it is possible to read out the reproduction data, so that tilt control can be performed based on jitter and error rate. Since the reproduction data cannot be read in the case of an unrecorded disc on which no is recorded, tilt control cannot be performed by this method. Further, even in the case of a partially recorded disc having an unrecorded portion, reproduced data cannot be read out in the unrecorded portion, and therefore tilt control based on jitter and error rate cannot be similarly performed in the unrecorded portion. . Here, the tilt control is necessary in the unrecorded portion when data is recorded in the unrecorded portion. However, if recording is performed in a state where the tilt control is not performed, the warpage of the disc on the inner and outer circumferences of the disc will occur. If they are different, the recording quality changes on the inner and outer circumferences.

In order to solve this inconvenience, conventionally, the level of the return optical signal when the pit has not yet been formed immediately after the recording power irradiation is sampled and held, and the tilt amount at which this sample hold value is maximized is adjusted. Accordingly, it is disclosed that tilt control can be performed in an unrecorded part during recording (see Patent Document 1). In addition, when the recorded part is reproduced, the tilt is controlled so as to minimize the jitter, and when the unrecorded part is recorded, the tilt amount is adjusted based on the focus error signal, so that the unrecorded part is recorded. Some have been disclosed to enable tilt control (see Patent Document 2). If the disc is a recorded disc, jitter is measured intermittently to correct the tilt of the objective lens. If the disc is not recorded, the warp of the disc is detected from the push-pull error signal and wobbling signal, and the objective is detected. Some have disclosed that lens tilt correction is performed (see Patent Document 3).
JP 2003-99965 A JP 2003-317288 A JP 2003-346369 A

  However, when the level of the return optical signal is sampled and held immediately after recording power irradiation and pits have not yet been formed, and the tilt amount is adjusted to maximize this sample hold value, the tilt of the unrecorded part is adjusted in advance. Since the amount cannot be detected, an OPC (Optimum Power Control) operation for determining the optimum recording power in a state where the optimum tilt is not achieved must be performed, and the optimum recording power cannot be accurately set by the OPC operation. Also, the tilt amount at the start of recording cannot be known, and tilt control immediately after the start of recording cannot be performed accurately. In addition, when tilt is controlled using a focus error signal, push-pull signal, or wobbling signal, the correlation with tilt differs depending on the device, and it is difficult to actually perform tilt control correctly. The reason for this is that these signals use the difference signal of the split detector that detects the return light of the disc, and thus are greatly influenced by the balance of the detector (position, output gain, etc.). Conceivable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc apparatus capable of accurately performing tilt control by performing tilt detection on an unrecorded disc in advance and accurately prior to actual recording.

In order to achieve the above object, the present invention provides an optical disc apparatus for recording data on an optical disc, wherein an encoder that generates a recording pulse and a peak power at the same level as a reproduction power that does not form a mark on the recording surface of the optical disc. And a laser power control means for supplying a control signal so as to drive the laser at a lower bottom power, and the peak power and the bottom power are set according to the control signal from the laser power control means, and the recording pulse And a laser driving means for driving the laser according to the above, and irradiating the unrecorded surface of the optical disc with laser light intensity-modulated with the recording pulse, and outputting a signal corresponding to the amount of return of the laser light from the unrecorded surface And an error rate or jitter of the signal output from the optical pickup. Characterized in that it has measuring means for measuring the data, a tilt adjusting means for adjusting the inclination of the optical axis of the laser beam relative to the optical disc in response to the error rate or jitter measured by the measuring means.

  The apparatus further includes storage means, wherein the measurement means measures error rates or jitters at a plurality of tilt angles, and the storage means minimizes the error rate or jitter measured by the measurement means. It is preferable that the tilt angle is stored as an optimum tilt angle, and the tilt adjustment unit adjusts the tilt of the optical axis of the laser beam with respect to the optical disc based on the optimum tilt angle read from the storage unit.

  Further, it is preferable that the measurement unit measures error rates or jitters at a plurality of positions in the disk radial direction, and the storage unit stores optimum tilt angles at the plurality of measurement positions.

  According to the present invention, an unrecorded surface of a disk is irradiated with laser light that is intensity-modulated according to a recording pulse with a peak power that does not form a mark on the recording surface of the optical disk and a bottom power that is lower than the peak power. Since the tilt is adjusted by measuring the error rate or jitter from the RF signal generated based on the return light from the recording surface, the tilt can be detected and controlled even on an unrecorded disc with the error rate and jitter. Is possible.

  Therefore, since the tilt amount of the unrecorded portion can be detected in advance before recording, the OPC operation for determining the optimum recording power in the optimum tilt state can be performed, and the optimum recording power setting by the OPC operation can be accurately set. Can be done. Jitter and error rate use the sum signal of the optical detector, so it is greatly influenced by the balance (position, output gain, etc.) of the detector compared to the focus error signal, push-pull signal, and wobbling signal. There is no end. In practice, when using jitter or error rate, the correlation with tilt is clearer than with focus error signal, push-pull signal, and wobbling signal, and the optimum tilt angle is known compared to using these signals. And accurate tilt control can be performed. In addition, since the tilt in the unrecorded portion can be controlled using the jitter or error rate as in the case of the recorded disc, there is no need to add additional hardware, and a different tilt adjustment routine also in the firmware There is no need to provide a simple structure, which is advantageous in terms of cost. Further, since data is not actually recorded on the disk recording surface, the recording capacity is not reduced for a write once recording disk, and unnecessary data is recorded for a rewritable disk such as a phase change type. There is no deterioration of the recording surface.

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

  <First Embodiment> FIG. 1 is a block diagram showing the configuration of an optical disk apparatus according to this embodiment.

  The disk 1 is mounted on a turntable 2 and is driven by a spindle motor 3 at CLV (constant linear velocity) or CAV (constant angular velocity). An optical pickup 4 is provided at a position facing the disk 1 and can be moved in the disk radial direction by a thread motor (not shown). The optical pickup 4 has a movable part 6 provided with an objective lens 5. The movable part is provided with a focus coil, a tracking coil, and a tilt coil, respectively, and a magnet and a yoke provided in the pickup. In addition, a magnetic circuit is configured (not shown).

  The laser light emitted from the laser diode 7 provided in the pickup is irradiated to the recording surface of the disk 1 through the objective lens 5, and the return light from the recording surface is detected by the photodetector 8 provided in the pickup. . The photodetector 8 has four detection surfaces A to D, and a focus error signal is generated from the difference (A + D) − (B + C) of the diagonal sum of the detection signals from the detection surfaces A to D. By applying a focus drive signal based on the focus error signal to the focus coil, focus control is performed so that the objective lens is driven in the focus direction and the laser beam is focused on the disk recording surface. A tracking error signal is generated from the difference (A + B) − (C + D) between the left and right detection signals of the detection surfaces A to D of the quadrant photodetector 8, and a tracking drive signal based on the generated tracking error signal is used as a tracking coil. In addition, the objective lens is driven in the tracking direction, and tracking control is performed so that the laser beam is positioned on the track of the disk.

  Further, the controller 10 has a storage unit 11 including a flash ROM or the like in which a tilt angle detected by a tilt detection operation described later is stored, and based on the tilt angle read from the storage unit. The controller 10 supplies a tilt control signal to the tilt drive circuit 19, and the tilt drive circuit 19 applies the tilt drive signal to the tilt coil, thereby driving the objective lens in the tilt direction of the disc to emit laser light to the disc. Tilt control is performed so that the axis is substantially vertical.

  A power control circuit 9 supplies a control signal to the laser driving circuit 12 so as to drive the laser 7 with a predetermined power in response to an instruction from the controller 10. Here, when a reproduction instruction is received from the controller 10, a control signal is supplied to the laser drive circuit 12 so as to drive the laser diode 7 with a predetermined constant reproduction power. When receiving a recording instruction, the control signal is sent to the laser drive circuit 12 so that the laser power is driven at a peak power that forms a mark on the disk recording surface and a bottom power that forms a space on the recording surface. Supply. When receiving an instruction from the controller 10 to detect the tilt angle of the recorded disc, a control signal is sent to the laser drive circuit 12 so as to drive the laser diode 7 at a predetermined constant reproduction power, as in reproduction. Supply. Further, when receiving an operation instruction for detecting the tilt angle of the unrecorded disc from the controller 10, the peak power (for example, 1 mW) which is the same as the reproduction power and does not form a mark on the recording surface and the bottom lower than this. A control signal is supplied to the laser drive circuit 12 so as to drive with power (for example, 0 mW).

  At the time of reproduction and at the time of detecting the tilt angle of the recorded disk, a laser beam having a power corresponding to an instruction from the controller 10 is irradiated from the laser diode 7 to the disk 1, and the reflected light from the disk is 4 through the half prism. The detection light detected by the divided photodetector 8 and received by each of the detection surfaces A to D is converted into an electrical signal, added, and then supplied to the RF signal processing unit 13. The RF signal processing unit 13 includes an RF detection circuit 14, a binarization circuit 15, and a PLL circuit 16. The RF detection circuit 14 includes a filter, an equalizer amplifier, and the like, and equalizes the waveform of the reproduced RF signal and supplies it to the binarization circuit 15. The binarization circuit 15 binarizes the reproduction equalized RF signal and supplies it to the PLL circuit 16. The PLL circuit 16 generates a synchronization signal from the binarized signal and supplies it to the decoder 17. The decoder 17 performs demodulation processing and error correction processing by ECC, and then supplies the reproduction data to the controller 10. Further, the decoder 17 supplies the error rate detected in the ECC decoding process to the controller 10. Demodulated data at the time of reproduction supplied to the controller 10 is output to a host device such as a computer (not shown).

  At the time of recording and in the tilt angle detection operation of the unrecorded disc, the recording data is supplied from the controller 10 to the encoder 18. The encoder 18 modulates the recording data and supplies a recording pulse to the laser driving circuit 12. Based on the control signal from the power control unit 9, the laser drive circuit 12 has a peak power enough to form a mark on the disk recording surface when the recording pulse from the encoder is Hi during the recording operation. When the recording pulse is low, the laser 7 is driven with a bottom power that forms a space on the recording surface. Further, during the tilt detection operation of the unrecorded disc, when the recording pulse from the encoder is Hi, the laser 7 is driven with a peak power of 1 mW which is the same as the reproduction power, and the recording pulse is Low. Drives the laser 7 with a bottom power of 0 mW lower than this. That is, the laser 7 is turned on / off according to the recording pulse. As described above, the laser driving circuit 12 performs intensity modulation on the laser light emitted from the laser diode 7 based on the recording pulse from the encoder, and performs recording on the optical disk. Alternatively, the disk surface is irradiated with a laser beam so that a pseudo RF signal is included in the reflected light of the disk.

  Next, the procedure of the tilt angle detection operation will be described based on the flowchart of FIG.

  First, the sled motor is driven to move the pickup to a predetermined position on the inner periphery of the disk (S101). Next, the tilt angle is set to an initial value (S102). Next, it is confirmed whether or not the position where the pickup 4 is moved is a recorded part or an unrecorded part (S103). The determination of whether the moved position is a recorded part or an unrecorded part is as follows. For example, if the RF signal is detected by replaying the part in advance, if the RF signal is detected, the part is a recorded part, and conversely, if it is not detected, it is determined that the part is an unrecorded part. . Further, by reading a TOC (Table Of Contents) area where the table of contents information is recorded, or by reading a PMA (Power Management Area) area where the record history information is recorded, the pickup movement position is recorded. Or whether it is an unrecorded part. If the movement position is the recorded part, a control signal is supplied to the laser drive circuit 12 so as to drive the laser 7 with a predetermined constant reproduction power, and the reproduction operation is started (S104).

  If the moving position is an unrecorded portion, the controller 10 drives the laser with a peak power (1 mW) that is the same as the reproduction power and does not form a mark on the recording surface, and a bottom power (0 mW) lower than this. The control signal is supplied to the laser driving circuit 12 and the encoder 18 is activated to generate a recording pulse. The laser driving circuit 12 intensifies the laser beam with the peak power and the bottom power set based on the recording pulse. Modulate and irradiate the disk (S105). The irradiated laser light is reflected by the recording surface of the disk, and this reflected light is detected by the photodetector 8. Since there is no pit on the disc in the unrecorded portion, the return light detected by the photodetector 8 is also a DC value with the reproduction power of DC emission, but the reproduction power is turned ON / OFF by the recording pulse from the encoder 18. Thus, an RF component can be included in the reproduction signal detected by the photodetector 8 as if there were pits on the disk. Here, by making the peak power the same as the reproduction power, it is possible to use the same parameter setting as in normal reproduction in the RF processing unit, and there is no need to reset the parameter again.

  Next, the error rate of the reproduction signal is measured (S106). When the error rate is measured, it is confirmed whether or not the tilt angle has reached a predetermined angle (for example, ± 20 minutes) (S107). If the angle does not reach the predetermined angle, the tilt angle is shifted by α (for example, 5 minutes) (S108), and the error rate is measured again. In this way, the error rate is measured in increments of α for the tilt angle. When the tilt angle reaches a predetermined angle, the tilt angle at which the error rate is minimized is calculated from the measurement result and stored (S109).

  The pseudo RF signal obtained from the reflected light of the unrecorded disc by turning the playback power ON / OFF is affected by the quality of the tilt and the error when the tilt angle is optimal, as with the playback RF signal obtained from the recorded disc. The rate is minimal. FIG. 3 shows the error rate when the tilt angle is changed every 5 minutes as described above. As shown in the figure, the error rate is minimized at the optimum tilt angle, and the error rate becomes worse as the distance from the optimum tilt angle increases. When obtaining the optimum tilt, the optimum tilt angle can be accurately obtained by quadratic approximation of the data and obtaining the vertex.

  When the optimum tilt angle is obtained, it is next checked whether or not the position of the pickup 4 has reached a predetermined position on the outer periphery of the disc (S110). If the predetermined position on the outer periphery has not been reached, the pickup 4 is moved in the outer peripheral direction by a predetermined amount (S111), and the operations of S102 to S109 are performed to obtain the optimum tilt angle at that position. These steps are repeated until it is reached. In this way, the optimum tilt angle at a plurality of positions on the disk is obtained while moving the position of the pickup 4.

  Here, as a plurality of positions on the disc, for example, the optimum tilt angle detection operation is performed at four points of the inner circumference, the middle circumference, the outer circumference, and the outermost circumference. Furthermore, by dividing into four zones of the inner, middle, outer and outermost zones and performing the tilt angle detection operation at a plurality of points in each zone, the tilt control at an arbitrary disk position can be performed accurately. . In this case, the degree of warpage of the disk increases as it goes to the outer periphery, so that the tilt angle detection position interval may be shortened toward the outer periphery. Further, in order to accurately determine the optimum recording power by the OPC operation, the tilt angle detection position on the inner circumference may be performed in a PCA (Power Calibration Area) area where the OPC operation is performed.

  <Second Embodiment> In the above case, the optimum tilt is set according to the error rate. However, it is also possible to set this by measuring the jitter.

  FIG. 4 is a block diagram showing the configuration of the optical disc apparatus according to this embodiment. In addition, the same number is attached | subjected about the same component as 1st Embodiment, and detailed description is abbreviate | omitted. The difference from FIG. 1 is that a jitter measurement circuit 21 is provided. The RF signal binarized by the binarization circuit 15 and the synchronous clock generated by the PLL circuit 16 are input to the jitter measurement circuit 21. In the jitter measurement circuit 21, jitter is measured by the phase difference between the binarized signal and the synchronous clock, and is output to the controller 10.

  Next, the procedure of the tilt angle detection operation will be described based on the flowchart of FIG. In FIG. 5, only the procedure of the tilt angle detection operation of the unrecorded disc is described, and the tilt angle detection operation of the recorded disc is omitted.

  Upon receiving a recording command for the first time, the controller 10 calculates the recording end position from the recording start position and the recording data amount (S201). Next, the thread motor is driven to move the pickup 4 to the recording start position on the disk (S202). Next, the tilt angle is set to an initial value (S203). Next, the controller 10 controls the laser driving circuit 12 to drive the laser at a peak power (1 mW) that is the same as the reproduction power and does not form a mark on the recording surface, and a bottom power (0 mW) lower than this. In addition to supplying a signal, the encoder 18 is activated to generate a recording pulse, and the laser driving circuit 12 modulates the intensity of the laser beam with the peak power and the bottom power set based on the recording pulse and irradiates the disk (S204). ).

Next, the jitter of the reproduction signal is measured (S205). When the jitter is measured, it is confirmed whether the tilt angle has reached a predetermined angle (for example, ± 20 minutes) (S206). If the angle does not reach the predetermined angle, the tilt angle is shifted by α (for example, 5 minutes) (S207), and jitter is measured again. In this way, jitter is measured with the tilt angle in increments of α. When the tilt angle reaches a predetermined angle, the tilt angle that minimizes the jitter is calculated from the measurement result, and this is stored (S208).
In the case of jitter, the same characteristics as in the graph of FIG. 3 showing the relationship between the error rate and the tilt angle are shown. The jitter is minimized at the optimum tilt angle, and the jitter gets worse as the distance from the optimum tilt angle is increased.

  When the optimum tilt angle is obtained, it is next checked whether or not the position of the pickup 4 has reached the recording end position (S209). If the recording end position has not been reached, the pickup 4 is moved in the outer circumferential direction by a predetermined amount (S210), and the operations of S203 to S208 are performed to obtain the optimum tilt angle at that position, and the pickup 4 reaches the recording end fixed position. These steps are repeated until. In this way, optimum tilt angles at a plurality of positions on the disc are obtained while moving the position of the pickup.

  In the above embodiment, since the optimum tilt angle from the recording start position to the recording end position is obtained, the tilt angle detection operation is performed only at the radial position where tilt control is required, so the time required for the tilt angle detection operation Can be shortened. Accordingly, when the distance from the recording start position to the recording end position is small, it is sufficient to detect the optimum tilt angle only at one radial position. Of course, the detection operation may be performed on the entire disk as in the first embodiment.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible.

  For example, in this embodiment, the peak power is set to 1 mW which is the same as the reproduction power, the bottom power is set to 0 mW, and the laser beam is intensity-modulated and irradiated to the disc. However, the peak power and the bottom power are applied to the disc recording surface. The detection sensitivity of the photodetector can be controlled by changing within a range that does not form a mark. For example, if the peak power is 1 mW and the bottom power is 0.5 mW, the edge detection sensitivity of the reproduction signal is deteriorated, and the error rate or jitter reacts sharply to the tilt angle as shown in FIG. Since the characteristics can be obtained, it becomes easier to obtain the optimum tilt angle.

1 is an overall configuration diagram of an optical disc device according to a first embodiment of the present invention. 3 is a process flowchart of the first embodiment of the present invention. It is a graph which shows the relationship between a tilt angle and an error rate. It is a whole block diagram of the optical disk apparatus concerning the 2nd Embodiment of this invention. It is a processing flowchart of a 2nd embodiment of the present invention. It is a graph which shows the relationship between the tilt angle at the time of changing laser power, and an error rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Disc 4 Optical pick-up 5 Objective lens 7 Laser diode 9 Power control circuit 10 Controller 12 Laser drive circuit 13 RF signal processing part 17 Decoder 18 Encoder 19 Tilt drive circuit 21 Jitter measurement circuit

Claims (3)

In an optical disc apparatus for recording data on an optical disc,
An encoder that generates a recording pulse;
Laser power control means for supplying a control signal so as to drive the laser at a peak power of the same level as the reproduction power that does not form a mark on the recording surface of the optical disc and a bottom power lower than this,
Laser driving means for setting the peak power and the bottom power in accordance with a control signal from the laser power control means, and for driving the laser according to the recording pulse;
An optical pickup that irradiates the unrecorded surface of the optical disc with laser light intensity-modulated with the recording pulse, and outputs a signal corresponding to the amount of return light of the laser light from the unrecorded surface;
Measuring means for measuring an error rate or jitter of the signal output from the optical pickup;
An optical disc apparatus comprising tilt adjusting means for adjusting an optical axis tilt of a laser beam with respect to the disk in accordance with an error rate or jitter measured by the measuring means. The apparatus of claim 1.
Furthermore, it has a storage means,
The measuring means measures an error rate or jitter at a plurality of tilt angles,
The storage means stores the tilt angle at which the error rate or jitter measured by the measuring means is minimized as the optimum tilt angle,
The optical disc apparatus characterized in that the tilt adjusting means adjusts the tilt of the optical axis of the laser beam with respect to the optical disc based on the optimum tilt angle read from the storage means. The apparatus of claim 2.
The measuring means measures error rate or jitter at a plurality of positions in the disk radial direction,
The optical disk apparatus, wherein the storage means stores optimum tilt angles at the plurality of measurement positions.

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