JP2008004152A - Optical disk device - Google Patents

Abstract

Data recording quality is improved by simple control.
An optical disc apparatus sets and stores a focus offset amount between a reproduction focus position and a recording focus position for each disc type in advance as a temporary offset amount. Then, when specifying the recording focus position, a temporary focus position A shifted by a temporary offset amount from the reproduction focus position acquired by a known technique is calculated. Then, data recording is performed while shifting the focus position in the plus direction and the minus direction with the provisional focus position A as a reference. Then, the peak level fluctuation amount of the RF sum signal at that time is monitored, and the position B where the fluctuation amount becomes small is specified as the recording focus position.
[Selection] Figure 2

Description

  The present invention relates to an optical disc apparatus that records or reproduces information by condensing a light beam and irradiating a storage surface of the optical disc.

  As is well known, in an optical disc apparatus that records and reproduces information by condensing a light beam and irradiating the storage surface of the optical disc, the light beam is placed at an appropriate position in order to perform suitable data reproduction and recording. It is necessary to focus on. Therefore, normally, the optical disc apparatus determines a focus position at which suitable data reproduction can be performed based on a tracking error signal value or the like. Further, it is known that the focus position suitable for reproduction and the focus position suitable for recording do not always match. Therefore, in general, the amount of deviation between the focus position suitable for playback and the focus position suitable for recording, the so-called focus offset amount, is set for each disc type, and only the focus offset amount from the playback focus position is set. Data recording is executed with the shifted position as the recording focus position. As described above, the focus control can be simplified by setting the focus offset amount from the reproduction focus position to the recording focus position in advance.

  However, the above method is simple, but has a problem that data recording quality may be lowered. That is, the focus position at which suitable data recording is possible is appropriately and slightly different depending on various conditions such as the optical pickup that irradiates the light beam, the individual difference of the optical disk, the data recording position (disk radius position), and the like. When the recording focus position is determined based on a preset focus offset amount, this individual difference or the difference in focus position due to the recording position cannot be reflected, resulting in a decrease in recording quality. In particular, in a multi-layer disc in which a plurality of recording layers are stacked, a focus position range in which suitable data recording is possible is narrow, and an allowable error amount is small. Therefore, the difference in individual and the difference in recording position have a great influence on the recording quality.

JP 2003-173549 A JP 2005-141851 A JP 2000-339727 A

  Therefore, many techniques have been proposed for obtaining a suitable focus offset amount (focus position) for each disk instead of using a uniformly defined focus offset amount. For example, Patent Documents 1 to 3 disclose a technique for obtaining a focus position used at the time of data recording or reproduction based on various parameter values obtained when operating while changing a focus position, a servo state, or the like. Has been. According to such a technique, it is possible to obtain an appropriate focus position that reflects differences in various conditions such as individual differences and recording positions of optical disks and optical pickups.

  However, all of these conventional techniques require a relatively complicated procedure for specifying the focus position. Therefore, there is a problem that the reproduction / recording quality is improved, but the control of the optical disc apparatus becomes complicated.

  By the way, the characteristics of the optical pickup are not uniform, and the relationship between the focus position and the signal value obtained by the optical pickup may differ depending on the type of the optical pickup. For example, some optical pickups vary the peak level fluctuation amount of the RF sum signal in synchronization with the focus servo residual during recording. In the case of an optical pickup having such characteristics, there is a possibility that focus control can be performed based on the peak level fluctuation amount of the RF sum signal. However, in the prior art, the difference in characteristics for each type of optical pickup has not been considered.

  Accordingly, an object of the present invention is to provide an optical disc apparatus capable of improving data recording quality with simple control.

  An optical disc apparatus according to the present invention, in an optical disc apparatus that records and reproduces information by condensing a light beam and irradiating a storage surface of the optical disc, is irradiated with a focus position varying unit that varies a focus position of the light beam. Based on the reflected light intensity reflected by the recording surface, the RF detection means for generating the RF sum signal and the data recording are executed while the focus position is changed by the focus position changing means when performing the data recording. And a focus position specifying means for specifying a focus position suitable for data recording as a recording focus position on the basis of the fluctuation amount of the peak level of the RF sum signal detected by the RF detection means at that time. To do.

  In a preferred aspect, the focus position specifying means changes the focus position with reference to a provisional focus position that is specified in advance in a simple manner. In this case, it further comprises storage means for storing the offset amount between the reproduction focus position and the recording focus position as a temporary offset amount for each disc type, and the focus position specifying means is configured to reproduce the reproduction focus position determined based on the reproduction quality. It is desirable to specify the position shifted by the temporary offset amount as the temporary focus position.

  In another preferred aspect, the focus position specifying means determines a direction in which the peak level fluctuation amount of the RF sum signal is reduced by moving the minute amount focus in the plus direction and the minus direction with reference to the provisional focus position, and the provisional focus. A position moved from the position by a distance obtained by multiplying the temporary offset amount by a predetermined coefficient in the decreasing direction is specified as the recording focus position.

  In another preferred aspect, the focus position specifying unit specifies a focus position at which the peak level fluctuation amount of the RF sum signal is equal to or less than a predetermined reference value as the recording focus position. In this case, it is desirable that the focus position specifying unit specifies the focus position where the peak level fluctuation amount of the RF sum signal is minimum as the recording focus position.

  In another preferred aspect, the focus position specifying means specifies the recording focus position every time a certain distance moves in the radial direction or every time a predetermined time elapses.

  According to the present invention, for each optical disc, the focus position suitable for data recording is specified as the recording focus position based on the fluctuation amount of the peak level of the RF sum signal, so that data recording can be performed at a suitable focus position. it can.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an optical disc apparatus according to an embodiment of the present invention.

  The optical disk 100 is clamped by a clamper and rotated at a high speed by a spindle motor 12. The optical pickup (PU) 14 is arranged to face the optical disc 100 and includes a laser diode (LD) that irradiates the surface of the optical disc 100 with laser light and a photodetector. The laser diode is driven by a laser diode drive circuit (LDD) 16 and irradiates a laser beam having a reproduction power when reproducing data, and irradiates a laser beam having a recording power when recording data. The photodetector of the optical pickup 14 outputs a detection signal corresponding to the state of the reflected light reflected by the recording surface to the RF detection unit 18 and the servo detection unit 20. As will be described in detail later, this optical pickup has a characteristic that the peak level fluctuation amount of the RF sum signal changes in accordance with the focus servo residual during data recording.

  The servo detection unit 20 generates a tracking error signal and a focus error signal based on the signal from the optical pickup 14 and outputs the tracking error signal and the focus error signal to the controller 32. The tracking error signal is generated by various known techniques such as a differential push-pull method, a phase difference method, and a three beam method. The focus error signal is also generated according to various known techniques such as an astigmatism method and a spot size method.

  The tracking control unit 24 drives the optical pickup 14 in the track width direction of the optical disc 100 so as to maintain the on-track state so that the position of the light beam in the track width direction becomes a position designated by the controller 32. Further, the focus control unit 26 performs focus control by driving the optical pickup 14 in the focus direction so that the focus position of the light beam becomes a position designated by the controller 32.

  The RF detection unit 18 amplifies the signal from the optical pickup 14, specifically the sum signal from the photodetector that receives the reflected light of the main beam, generates a reproduction RF signal, and outputs it to the decoder 30 and the controller 32.

  The decoder 30 includes an equalizer and a binarizer, boosts and binarizes a predetermined frequency of the reproduction RF signal, specifically, the amplitude of the 3T signal, demodulates the binarized signal, and outputs the demodulated signal to the controller 32. Demodulation is performed by generating a synchronous clock signal by a PLL circuit (not shown) and extracting the signal. The decoder 30 detects jitter by adding the phase difference between the binarized signal and the synchronous clock, and supplies the detected jitter to the controller 32.

  The controller 32 controls each part of the optical disk device 10 based on a drive command from a user or a host device. Further, various control parameter values necessary for control are obtained based on the RF sum signal value, jitter value, and the like input from the decoder 30 and the RF detector 18. Here, one of the control parameters required by the controller 32 is a focus position. Prior to actual data reproduction and recording, the controller obtains a reproduction focus position suitable for reproduction and a recording focus position suitable for recording, and data is recorded and reproduced at the determined focus position.

  In the present embodiment, the reproduction focus position is obtained using a known publicly known technique. The recording focus position is based on the fluctuation amount of the RF sum signal when data recording is performed while shifting the focus position with reference to the reproduction focus position and the temporary focus position obtained by a predetermined temporary offset amount. Looking for. The specific contents of how to obtain the recording focus position will be described in detail later.

  The memory 34 stores various parameters necessary for optical disk drive control. The memory 34 also stores a temporary offset value for each disk type. As will be described in detail later, the provisional offset amount is a difference between the reproduction focus position and the recording focus position, and a focus offset amount. However, the temporary offset amount stored in the memory is only a temporary value, and the temporary offset amount is only used as a reference when specifying the actual recording focus position.

  Next, specific specific contents of the recording focus position by the optical disc apparatus 10 will be described. As described above, the optical disc apparatus 10 of this embodiment sets and stores the offset amount between the reproduction focus position and the recording focus position for each disc type. However, the offset amount specified here is only a temporary focus offset amount, and reflects the difference in focus position caused by the individual difference of each optical disk or optical PU 14 and the difference in data recording position (disk radius position). Not a value.

  However, conventionally, a position shifted from the reproduction focus position by the offset amount (temporary offset amount) set for each disc type has been specified as the recording focus position. However, as described above, the focus offset amount set in advance is not a value that reflects the individual difference between the optical disc and the optical PU 14, and therefore, suitable data recording cannot be performed at the storage focus position specified by the method. was there. In particular, in a multi-layered optical disk with a narrow focus range that allows suitable data recording, the effect of this individual difference on the accuracy of the recording focus position is large, and the recording focus determined based on a uniformly determined offset amount. In many cases, suitable data recording could not be performed at the position. Further, the focus position at which suitable data recording is possible differs greatly depending not only on the individual difference of the disk or the like but also on the data recording position (disk radius position). For this reason, it is difficult to perform suitable data recording with the conventional technique in which only a single focus offset amount (temporary offset amount) is set for one disc.

  Therefore, in this embodiment, the temporary focus position is corrected for each disk or for each predetermined data recording position, and a suitable recording focus position is specified. That is, when specifying the recording focus position, the controller drives each unit to specify the reproduction focus position first. The reproduction focus position is specified by a known publicly known technique, for example, a technique of performing data reproduction while shifting the focus position and specifying the position where the obtained RF sum signal value is maximum or the jitter value is minimum as the reproduction focus position. Can be used.

  If the reproduction focus position can be specified, a position obtained by shifting the reproduction focus position by the temporary offset amount is calculated as the temporary focus position. Then, data recording is performed while shifting the focus position in the plus direction (back side when viewed from the light PU) and the minus direction (front side when viewed from the light PU) with the temporary focus position as a reference. During this data recording, the controller detects the peak level of the RF sum signal value detected by the RF detector and temporarily stores the value in the memory. Here, the optical PU 14 used in this embodiment has a characteristic that the peak level of the RF sum signal obtained at the time of recording varies in synchronization with the residual of the focus servo. In other words, in the optical PU 14, when the fluctuation of the peak level of the RF sum signal is small, the residual of the focus servo is small, and it can be said that high-quality data recording can be performed stably. Therefore, the controller finds a position where the amount of fluctuation of the RF sum signal value generated with the shift of the focus position is minimized, and specifies this as the recording focus position.

  FIG. 2 is a diagram illustrating the relationship between the focus position and the peak level fluctuation amount of the RF sum signal. In FIG. 2, the horizontal axis indicates the focus position, and the vertical axis indicates the amount of fluctuation in the peak level of the RF sum signal value.

  In FIG. 2, it is assumed that the temporary focus position shifted from the reproduction focus position by a preset temporary offset amount is point A. In this state, when the recording focus position is specified, the controller 32 moves the focus position slightly in the plus direction and the minus direction by using the temporary focus position A as a reference. In the illustrated example of FIG. 2, it can be seen that the peak level fluctuation amount of the RF sum signal increases as the focus position is moved in the plus direction and decreases as the focus position is moved in the minus direction. Accordingly, in this case, the controller 32 sequentially shifts the focus position from the temporary focus position A in the minus direction, and specifies the point B at which the peak level fluctuation amount of the RF sum signal is the minimum as the recording focus position.

  In this way, by specifying the temporary focus position on the basis of the peak level fluctuation amount of the RF sum signal for each disk or for each predetermined data recording position, individual differences of optical disks and optical PUs, data recording An appropriate recording focus position reflecting the position difference can be obtained. As a result, high quality data recording is possible. The recording focus position is specified based on the temporary focus position that is simply obtained based on the temporary offset amount and the reproduction focus position. For this reason, the amount of movement of the focus position that is shifted to specify the recording focus position is reduced, and a suitable recording focus position can be specified easily in a relatively short time.

  In the above description, the position at which the peak level fluctuation amount of the RF sum signal is minimized is specified as the recording focus position. However, if the data can be recorded with quality higher than a certain standard, the position is not necessarily the minimum position. May be. For example, a position where the peak level fluctuation amount of the RF sum signal is equal to or less than a predetermined threshold value may be specified as the recording focus position. Alternatively, a position moved by a distance obtained by multiplying the temporary offset amount by a predetermined coefficient may be specified as the recording focus position. For example, consider the case where the temporary focus position A is obtained from the reproduction focus position and the temporary offset position as shown in FIG. At this time, in order to specify the recording focus position, the controller 32 slightly shifts the focus position in each of the minus direction and the plus direction with the temporary focus position A as a reference. As a result, it can be seen that the peak level fluctuation amount of the RF sum signal decreases with the shift in the plus direction. In this case, the controller 32 specifies, as the recording focus position, the position B that is moved in the plus direction by an amount obtained by multiplying the temporary offset amount F by a predetermined coefficient n%.

  Further, as shown in FIG. 4, the temporary focus position A obtained based on the reproduction focus position and the temporary offset amount may be the minimum position of the peak level fluctuation amount of the RF sum signal value. In this case, regardless of whether the focus is moved in the plus direction or the minus direction from the temporary focus position A, the RF sum signal value peak level fluctuation amount increases. Therefore, in this case, the controller 32 specifies the temporary focus position A as the recording focus position.

  Next, the flow of determining the recording defocus amount in this optical disc apparatus will be described with reference to FIGS. When the optical disk 100 is mounted on the optical disk device 10 (S10), the controller 32 drives the optical PU 14, the RF detection unit 18, the decoder 30, and the like to specify the disk type of the mounted optical disk 100 (S12). . Further, the temporary offset amount corresponding to the mounted optical disc 100 is specified with reference to the information on the temporary offset amount set for each disc type recorded in the memory 34 (S12). The specified temporary offset amount is temporarily stored in the memory 34.

  Thereafter, the intensity of the laser beam, the reproduction focus position, and the like are determined using a known technique by an operation such as OPC (S14).

  If the reproduction focus position is determined, then the recording focus position is determined (S16). A specific detailed flow of this recording focus position is shown in FIG. When specifying the recording focus position, first, the temporary focus position shifted from the already specified reproduction focus position by the temporary offset amount temporarily stored in the memory 34 is calculated (S30). Subsequently, data recording is started while gradually moving the focus position in the plus direction from the calculated temporary focus position (S32). At this time, the controller 32 determines whether the fluctuation amount of the peak level of the obtained RF sum signal tends to decrease or increases (S34).

  When the fluctuation amount of the peak level of the RF sum signal decreases, it can be said that the residual of the focus servo also decreases in synchronization. Accordingly, when the fluctuation amount of the peak level of the RF sum signal decreases, in this case, the focus position is moved in the plus direction until the fluctuation amount of the peak level of the RF sum signal takes the minimum value (S36). If the peak level fluctuation amount of the RF sum signal reaches the minimum value, the focus position at that time is specified as the recording focus position (S44).

  On the other hand, if it is determined in step S34 that the fluctuation amount of the peak level of the RF sum signal has increased, it is expected that the level fluctuation amount will not decrease even if the focus position is further moved in the plus direction. Therefore, in this case, data recording is performed by gradually moving the focus position in the minus direction (S38). Then, the peak level fluctuation amount of the RF sum signal at that time is monitored. The controller 32 determines whether or not the peak level fluctuation amount of the RF sum signal decreases with the movement in the minus direction (S40).

  When the peak level fluctuation amount of the RF sum signal decreases, the controller 32 continues to move the focus position in the minus direction until the fluctuation amount becomes the minimum value (S42). Then, the focus position at the time when the peak level fluctuation amount of the RF sum signal becomes the minimum value is specified as the recording focus position (S44).

  On the other hand, when the peak level fluctuation amount of the RF sum signal increases (No in S34 and No in S40) regardless of whether the focus position is moved in the plus direction or the minus direction, the RF signal at the time of the temporary focus position. It can be estimated that the peak level fluctuation amount of the sum signal is the minimum value. Therefore, in this case, the temporary focus position obtained from the reproduction focus position and the temporary offset amount is directly specified as the recording focus position (S46).

  If the recording focus position can be determined by the above procedure, data recording is executed at the focus position (see FIG. 5, S18). However, it is known that the relationship between the focus position and the recording quality appropriately changes depending on the data recording position (disk radius position). Therefore, even if the recording focus position is once determined, the recording focus position is specified again every time the recording focus position moves in the radial direction (S20, S18). As a result, even if the focus position at which suitable data recording is possible due to a difference in recording position is changed, the correction can be performed, and data recording at a suitable focus position can always be performed. As a result, the data recording quality can be improved.

  In this case, the recording focus position is specified every time when it moves a predetermined distance in the radial direction, but naturally the operation of specifying the recording focus position may be performed at another timing. For example, the recording focus position specifying operation may be performed every predetermined time. That is, the criterion in step S20 in FIG. 5 may be the elapsed time instead of the movement distance. Further, instead of repeatedly specifying the recording focus position, the recording focus position specified first may be used to the end. That is, the processing flow may omit the step S20 in FIG.

  FIG. 6 illustrates the flow when the position where the peak level fluctuation amount of the RF sum signal is the minimum is set as the recording focus position (see FIG. 2). However, as described with reference to FIG. 3, the position where the peak level fluctuation amount of the RF sum signal is not necessarily required to be the recording focus position. Therefore, as described with reference to FIG. 3, the position moved by a predetermined amount in the direction in which the peak level fluctuation amount decreases may be specified as the recording focus position.

  As described above, according to the present embodiment, the recording focus position is specified based on the peak level fluctuation amount of the RF sum signal when data recording is performed while changing the focus position. As a result, the quality of data recording can be improved. Further, when the recording focus position is specified, the focus position is shifted with reference to a roughly determined temporary focus position. Therefore, the amount of movement of the focus position until the recording focus position is reached can be reduced, and a suitable recording focus position can be easily specified in a relatively short time.

1 is a diagram showing a schematic configuration of an optical disc apparatus according to an embodiment of the present invention. It is an example which shows the relationship between a temporary focus position and a recording focus position. It is another example which shows the relationship between a temporary focus position and a recording focus position. It is another example which shows the relationship between a temporary focus position and a recording focus position. It is a flowchart which shows the flow in the case of specifying a recording focus position. It is a flowchart which shows the detail of step S16 in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Optical disk apparatus, 12 Spindle motor, 14 Optical PU, 18 RF detection part, 20 Servo detection part, 24 Tracking control part, 26 Focus control part, 30 Decoder, 32 Controller, 34 Memory

Claims (8)

In an optical disc apparatus that records and reproduces information by condensing a light beam and irradiating the storage surface of the optical disc,
Focus position varying means for varying the focus position of the light beam;
RF detecting means for generating an RF sum signal based on the reflected light intensity of the irradiated light beam reflected by the recording surface;
When data recording is performed, the data recording is performed while the focus position is changed by the focus position changing unit, and data recording is performed based on the amount of change in the peak level of the RF sum signal detected by the RF detection unit at that time. A focus position specifying means for specifying a suitable focus position as a recording focus position;
An optical disc apparatus comprising: The optical disc apparatus according to claim 1,
An optical disc apparatus characterized in that the focus position specifying means changes the focus position on the basis of a provisional focus position that is simply specified in advance. The optical disk device according to claim 2, further comprising:
Storage means for storing the offset amount between the reproduction focus position and the recording focus position as a temporary offset amount for each disc type;
An optical disc apparatus characterized in that the focus position specifying means specifies a position shifted by a temporary offset amount from the reproduction focus position determined based on the reproduction quality as the temporary focus position. The optical disc apparatus according to claim 2 or 3,
The focus position specifying means determines a direction in which the peak level fluctuation amount of the RF sum signal is decreased by moving the minute amount of focus in the plus direction and the minus direction with reference to the temporary focus position, and in the direction of decreasing from the temporary focus position. An optical disc apparatus characterized in that a position moved by a distance obtained by multiplying a provisional offset amount by a predetermined coefficient is specified as a recording focus position. The optical disk device according to any one of claims 1 to 3,
An optical disc apparatus characterized in that the focus position specifying means specifies a focus position at which the peak level fluctuation amount of the RF sum signal is not more than a predetermined reference value as a recording focus position. The optical disc apparatus according to claim 5, wherein
An optical disc apparatus characterized in that the focus position specifying means specifies the focus position where the peak level fluctuation amount of the RF sum signal is minimum as the recording focus position. The optical disk device according to any one of claims 1 to 6,
An optical disc apparatus characterized in that the focus position specifying means specifies a recording focus position every time the focus position specifying means moves a certain distance in the radial direction. The optical disk device according to any one of claims 1 to 6,
An optical disc apparatus characterized in that the focus position specifying means specifies a recording focus position every predetermined time.

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