JP2006268951A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device capable of highly accurately determining which of the signal surface or the cover surface of an optical disk focus servo is applied to. <P>SOLUTION: When an optical disk has a fixed or more eccentricity, as the number of tracks detected by optical means 20 is several hundreds to several thousands and the number of noises is about several tens, when it is detected that a track count n is less than 1/10 of a premeasured reference track count N, the application of focus servo on the cover layer of the optical disk 10 is determined, and the application of focus servo on a signal layer is determined when not less than. Thus, even when noises are detected while the focus servo is applied on the cover layer, the noises and tracks are determined. Accordingly, track detection accuracy is improved more than before. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that reproduces or records information recorded on a track of an optical disc, and more particularly to an optical disc apparatus that determines with high accuracy whether a signal servo or a cover surface of an optical disc has been subjected to focus servo.

  In an optical disc apparatus represented by a compact disc player, a video disc player, and the like, a focusing control mechanism, a tracking control mechanism, and the like are provided as functions for reproducing or recording information recorded on the optical disc.

  These mechanisms are mechanisms that move the objective lens to a predetermined position on the track of the optical disc and cause the light beam to converge and follow the signal surface of the optical disc through the objective lens. I'm calling.

  The focus error signal used for this focus servo control is a signal that is output only when the optical disc is in focus, and its signal characteristics have an S-shaped curve centered on the in-focus as shown in FIG. is doing. This S-shaped curve characteristic has a substantially straight line shape in the vicinity of the in-focus point ("straight line area" in FIG. 7), but as it goes beyond the straight line area and away from the optical disk or toward the optical disk. The focus error signal is zero.

When reproducing or recording information recorded on the optical disc, it is necessary to control so that the focus error signal always falls within the linear region of the S-shaped curve characteristic. Therefore, the signal is selected in advance so that the focus error signal falls within the linear region (about ± 4 to 8 μm), and this signal is amplified and applied to the focus coil, so that the focus error signal approaches the focal point. In this way, by controlling the movement of the objective lens, information is reproduced or recorded by performing fine adjustment so as to always fall within the linear region of the S-shaped curve characteristic. In the S-curve characteristic shown in FIG. 7, when the focus error signal advances in the direction of approaching zero beyond the linear region, it means that the objective lens is moving away from the track to be detected. Such a focus servo system is described in detail in Patent Document 1.
JP-A-5-109085

  By the way, the S-curve characteristic is normally output when the laser is focused on the signal surface, but also when no information is recorded, that is, when the laser is focused on the surface of the cover layer. There is a problem of being output.

  This phenomenon will be described with reference to FIG. FIG. 8 is a cross-sectional view of the optical disc 100. As shown in the figure, an optical disc 100 is a disc-shaped transparent disc substrate 101 made of a transparent resin material, and a signal layer 102 and a cover layer (also referred to as a protective layer) 103 that are laminated on the transparent disc substrate 101. A disc having at least On the surface of the cover layer 103, a track is formed in which uneven pits are spirally or concentrically arranged, and a metallic reflective film such as aluminum is formed on the surface so as to cover the signal surface 102a. Is formed.

  When the information recorded on the signal surface 102a is reproduced, the laser beam L1 is converged via the objective lens OB1, irradiated onto the track, reflected by the pit, and returned to the same axis as the irradiated light. Information is read by separating the light with a half mirror (not shown).

  Here, when detecting a track in order to irradiate the track with a laser beam, the objective lens OB1 is moved in the vertical direction of the optical disc surface in accordance with a control command of the focusing control mechanism. At this time, as shown in FIG. 8A, the focus error signal having the S-curve characteristic shown in FIG. 7 is detected on the assumption that the track detection is normally performed when the laser is focused on the signal surface 102a. However, as shown in FIG. 8B, the focus error signal may be detected even when the laser is focused on the surface of the cover layer 103 (hereinafter simply referred to as the cover surface 103a).

  Up to now, as shown in FIG. 9, the amplitude A (characteristic A) of the focus error signal detected by focusing on the signal surface 102a and the focus error signal detected by focusing the laser on the cover surface 103a. Since the difference in amplitude B (characteristic B) (the amplitude of characteristic A−the amplitude of characteristic B) was very large, it was possible to determine which surface was focused based on the difference between the two amplitudes. Similarly, even in a single-layer blue laser optical disc that has become widespread in recent years, the difference between the amplitude of the focus error signal detected from the signal surface 102a and the amplitude of the focus error signal detected from the cover surface 103a is 1/5. Since there was a degree, it was possible to determine which one was in focus.

  However, the S-curve characteristic of the focus error signal changes depending on the reflectance of the signal surface 102a, the optical aberration of the laser beam, and the like. For example, when a blue laser double-layer optical disk is reproduced or recorded by a conventional method, the difference in reflectance between the signal surface 102a and the cover surface 103a is very small, and there is almost no amplitude difference. It was very difficult to determine whether the subject was in focus.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical disc apparatus capable of accurately determining which of the signal surface and the cover surface of the optical disc has focus servo applied. .

  In order to solve the above-mentioned problems, the present invention according to claim 1 includes an objective lens for condensing a light beam on a track on an optical disk, light detection means for detecting at least reflected light reflected from the track on the optical disk, Tracking error signal generation means for calculating a positional deviation between the irradiation position of the light beam and the track from the optical signal detected by the light detection means and generating a tracking error signal, and in the cross direction of the track based on the tracking error signal An optical disc apparatus including at least a tracking drive unit that moves the objective lens, and a signal correction unit that corrects the tracking error signal if the tracking error signal and superimposed noise are equal to or greater than a certain threshold, and a signal correction unit. Count the number of tracks based on the corrected tracking error signal Counting means, storage means for storing the number of tracks detected when the optical disk is rotated for a certain period of time as a reference track number, and detection of information recorded on the optical disk within a period of time equivalent to a certain period of time The number of tracks to be measured is the number of measured tracks, and the comparison means compares the number of reference tracks with the number of measured tracks. The gist of the present invention is to include a determination unit that determines that the servo is applied and determines that the focus servo is applied to an area where the track of the optical disk exists when the number of measured tracks is equal to or greater than the reference number of tracks.

  In order to solve the above-mentioned problem, the present invention according to claim 2 is configured such that when the determination unit determines that the number of measurement tracks is less than the reference number of tracks, the objective lens is moved at a constant speed in a direction crossing the tracks of the optical disk. The gist of the invention is to provide a tracking control means for outputting a drive signal for moving in a specific one direction to the tracking drive means.

  According to the present invention, it is possible to determine with high accuracy whether the focus servo is applied to the signal surface of the optical disc or the cover layer. Therefore, even if the focus servo is accidentally applied to the surface of the cover layer, the retry operation is performed immediately after detection. Therefore, it is possible to provide an optical disc apparatus that improves the efficiency of reading information from the optical disc.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

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

  This optical disk apparatus includes an optical disk 10 that is set to be freely rotatable by a spindle motor 11, optical means 20 that irradiates a track formed on the optical disk 10 with a laser beam, and detects reflected return light, and this optical means. The optical signal detected at 20 is separated into a focus error signal and a tracking error signal to correct the signal level to an appropriate value, and based on the signal corrected by the signal correction means 30, the optical means 20 At least a calculation / control unit 40 that calculates the movement amount in the focus direction and the track direction, and a drive unit 50 that moves the optical unit 20 in the focus direction and the track direction according to the movement amount calculated by the calculation / control unit 40 I have.

  Here, in the present embodiment, the optical disc 10 is specifically a CD (Compact Disc), an MD (Mini Disc), a DVD (Digital Video Disc (including DVD-R, DVD-RW)), an ultra-high density. It is a general term for optical disks.

  On the other hand, the optical means 20 includes an objective lens 21 for condensing a laser beam on a track formed on the surface of the optical disc 10, and a photodetector (not shown) for detecting reflected return light reflected by the track. A focus actuator 22 that moves the objective lens 21 and the photodetector in the focus direction and a tracking actuator 23 that moves the objective lens 21 and the photodetector in the cross direction of the track are provided.

  The signal correction unit 30 includes a signal calculation unit 31, a gain / offset correction FEP 32, a focus A / D 33, a tracking A / D 34, a bandpass filter 35 (hereinafter simply referred to as a BPF 35), and a hysteresis comparator 36. At least.

  The signal calculation unit 31 provided in the signal correction unit 30 obtains the focus error signal and the tracking error signal separately from the signal detected by the photodetector built in the optical unit 20 and corrects these signals by gain / offset correction. This is a functional unit that outputs to the FEP 32 for use.

  The gain / offset correction FEP 32 is a functional unit for performing amplitude and offset settings in advance in order to generate a focus error signal and a tracking error signal suitable for the focus A / D 33 and the tracking A / D 34 connected to the subsequent stage. . The tracking error signal corrected by the gain / offset correction FEP 32 is also output to a band pass filter (hereinafter referred to simply as BPF) 35.

  The focus A / D 33 and the tracking A / D 34 are functional units for converting the focus error signal and the tracking error signal from an analog signal to a digital signal, respectively.

  The BPF 35 is a functional unit that removes low-frequency offset fluctuations and noise. As an example of the low-frequency offset fluctuation, there is an offset fluctuation that coincides with the disk cycle generated by the eccentricity of the optical disk.

  The hysteresis comparator 36 is a comparator with improved noise resistance. By giving a predetermined threshold (threshold) a certain width, the degree of influence of noise superimposed on a specific frequency on this frequency. It is a functional part for lowering. A signal exceeding a threshold having a certain width is regarded as a signal (number of tracks) for detecting a track, and is output to a determination unit 43 described later.

  Next, a specific configuration of the calculation / control unit 40 will be described. The calculation / control unit 40 includes at least a focus control unit 41, a tracking control unit 42, a determination unit 43, and a servo control unit 44.

  The focus control unit 41 acquires a focus error signal after digital signal conversion from the focus A / D 33, and outputs a focus control signal to the driving unit 50 in response to an output command from a servo control unit 44 described later. Part.

  Similarly to the focus control unit 41, the tracking control unit 42 acquires a tracking error signal after digital signal conversion from the tracking A / D 34, and tracks the driving unit 50 in accordance with an output command from the servo control unit 44. It is a functional unit that outputs a control signal.

  The determination unit 43 obtains the number of tracks from the hysteresis comparator 36, counts the number of tracks existing in a certain measurement section, and determines whether the number of tracks is less than a pre-stored reference number of tracks. It is a function part which determines. If it is detected that the number of tracks is less than the pre-stored reference number of tracks, it is determined that focus servo has been applied to an area without a track (ie, the cover layer), and the servo controller 44 determines that. Notify the result. For example, a “track non-detection flag” is output to the servo control unit 44.

  The servo control unit 44 is a functional unit that monitors and controls the focus control unit 41, the tracking control unit 42, the determination unit 43, and other functional units not shown. In particular, when a comparison result is acquired from a track counter comparison unit 433 provided in the determination unit 43 to be described later, a reset signal is output to the track counter 431 and the section counter 432, and a control process is performed to prepare for the next determination.

  Here, a specific configuration of the determination unit 43 described above will be described with reference to FIG.

  The determination unit 43 includes at least a track counter 431, a section counter 432, a track counter comparison section 433, and a section counter comparison section 434.

  The track counter 431 obtains a hysteresis signal exceeding a threshold having a certain width from the hysteresis comparator 36, and detects the rising edge (or falling edge) of this signal, thereby counting the number of tracks. The counted number of tracks is output to the track counter comparison unit 433.

  The interval counter 432 is a functional unit that measures a measurement interval by acquiring a sampling frequency from the sampling clock 60 and counting rising edges (or falling edges) of this frequency. The counted section count number is output to the section counter comparison unit 434.

  The section counter comparison unit 434 compares the section count number acquired from the section counter 432 with a reference section count number stored in advance, and when the section count number reaches the reference section counter number, the section counter comparison unit 433 A comparison start signal is output.

  When the track counter comparing unit 433 acquires the comparison start signal from the section counter comparing unit 434, the track counter comparing unit 433 acquires the track count number from the track counter 431, and compares the reference track number stored in advance with the track count number. As a result of the comparison, if the track count number is equal to or exceeds the reference track number within a predetermined measurement section, it is determined that the focus servo has been applied to the signal layer and the servo control unit 44 is informed of the “track detection flag. Is output. On the other hand, when the track count number is less than the reference track number, it is determined that the focus servo is applied to the area without the track (that is, the cover layer), and the “track non-detection flag” is output to the servo control unit 44. To do.

  Here, in this embodiment, the determination criterion is based on whether or not the actually measured number of tracks is less than the reference number of tracks. However, the determination criterion is not limited to this, and the actual number of tracks is less than the reference number of tracks. It may be determined whether or not it is 1/10 or less. By specifying the determination criteria, it is possible to detect with higher accuracy whether the focus servo is applied to the signal surface or the cover surface of the optical disk.

  Here, the reason why the criterion is set to 1/10 will be described. First, when the optical disk 10 is set to the spindle motor 11 and rotated, if this setting is set in an ideal state, that is, in a state where no eccentricity occurs, it is detected with one rotation of the optical disk 10. The number of tracks is one. However, in reality, a minute eccentricity is generated or noise is superimposed due to a design / processing error of the spindle motor 11 or the optical disk hole. Therefore, several hundred tracks are usually detected with one rotation of the optical disk.

  Until now, in order to distinguish the signal layer from the cover layer, it has been determined that the track has been detected, that is, that the signal layer has been subjected to focus servo. However, in reality, hundreds of tracks and signals with superimposed noise are detected, so the signal with noise superimposed is erroneously judged to be a track even though the focus servo is applied to the cover layer. was there. Therefore, there is a need to distinguish between noise and track.

  Accordingly, the inventors of the present application have confirmed that the noise generated with one rotation of the optical disk when the optical disk 10 is set to the spindle motor 11 is about several tens of noises no matter how it is set. I found it. The number of tracks is detected at the level of several hundreds as described above, but the number of signals when the focus servo is applied to the cover layer and noise is detected therefrom is clearly different from the number of tracks, and the number of signals is several tens. Degree. Therefore, the number of tracks counted at the time of normal detection is set as a reference value (that is, several hundred tracks as a reference value), and when it is less than 1/10 of this reference value, it is determined that the noise is detected. Tracks can be distinguished. Therefore, by setting this determination criterion in the determination unit 43, it is possible to realize highly accurate determination.

  Returning to FIG. 1, the description of the driving means 50 will be continued. The driving unit 50 includes at least a focus actuator D / A 51, a tracking actuator D / A 52, a focus actuator driver 53, and a tracking actuator driver 54.

  Here, the focus actuator D / A 51 and the tracking actuator D / A 52 obtain a focus control signal and a tracking control signal from the focus control unit 41 and the tracking control unit 42, respectively, and convert these signals from a digital signal to an analog signal. Part.

  The focus actuator driver 53 and the tracking actuator driver 54 output drive signals to the focus actuator 22 and the tracking actuator 23 built in the optical means 20 based on the analog-converted signal, and the focus actuator 22 and the tracking actuator 23. Is a functional unit that moves the button in a predetermined direction.

  Next, focus servo and track control operations of the optical disk apparatus having the above-described configuration will be described.

  First, the optical disk 10 is set in the spindle motor 11. When an optical disk playback command is input from the outside of the optical disk apparatus, the spindle motor 11 starts driving, the optical disk rotates, and the photodetector moves to the optical disk reading start point. When the reading start point is determined, a reproduction laser beam is output from the optical means 20. The laser beam is condensed at the reading start point of the optical disc 10 through the objective lens 21 and reflected by the pit formed at this position. The reflected return light is again taken into the photodetector through the objective lens 21, separated by a half mirror built in the photodetector, and output to the signal calculation unit 31.

  The separated reflected return light is separated into a focus error signal and a tracking error signal by the signal calculation unit 31, and both signals are output to the gain / offset correction FEP 32. When the focus error signal and the tracking error signal are converted into digital signals by the gain / offset correction FEP 32, the amplitude and the offset are suitable for the focus A / D 33 and the tracking A / D 34 connected to the subsequent stage. The signal is corrected.

  The amplitude-processed and offset-processed signals are output to the focus A / D 33 and tracking A / D 34, respectively. Here, the tracking error signal is further divided and output to the BPF 35.

  After the focus error signal is converted into a digital signal by the focus A / D 33, the focus error signal is output to the focus control unit 41 and continues to be held until an instruction signal from the servo control unit 44 is input. When an output instruction is received, a focus control signal is output to the focus actuator D / A 51. This signal is transmitted to the focus actuator 22 via the focus actuator driver 53, and the optical means 20 including the objective lens 21 is moved in the focus direction by a predetermined amount.

  Similarly, after the tracking error signal is converted into a digital signal by the tracking A / D 34, the tracking error signal is continuously held until it is output to the tracking control unit 42 and the output command of the servo control unit 44 is input. When an output instruction is received from 44, a tracking control signal is output to the tracking actuator D / A 52. This signal is transmitted to the tracking actuator 23 via the tracking actuator driver 54, and moves the optical means 20 including the objective lens 21 by a predetermined amount in the cross direction of the track. With the above operation, information is read from a predetermined position on the optical disc 10, and when this reading is completed, the reading operation is sequentially repeated by moving the objective lens 21 to the next reading position.

  Here, a specific determination method for determining the signal layer and the cover layer in the operation of the optical disc apparatus will be described with reference to FIG. FIG. 3 is a flowchart showing this determination method.

  This determination method is an operation performed in addition to the basic operation of the optical disc apparatus, and improves the detection of the signal layer by combining the operations of the determination unit 43 shown in FIG. Therefore, the description of the basic operation of the optical disc apparatus described above will be omitted, and the description will be made focusing on the operation of the determination unit 43.

  As shown in FIG. 3, when the optical disk 10 is set in the spindle motor 11 and a reproduction or recording command is input from the outside of the optical disk apparatus, the servo control unit 44 outputs a reset signal to the track counter 431 and the section counter 432. The counter values are initialized (step S1).

  The interval counter 432 starts acquiring a clock signal from the sampling clock 60, detects an edge every time one clock is acquired, and adds 1 to a preset variable t when an edge is detected. In the section counter 432, t = t + 1 is set and stored in advance as an addition formula for the variable t (step S2). At this stage, “1” is held in the variable t.

  On the other hand, the track counter 431 constantly monitors the output of the hysteresis comparator 36. When the change in the output of the hysteresis comparator 36 is detected (that is, when it is detected that the signal-corrected tracking error signal is output), this signal is output. 1 is detected and 1 is added to the variable n of the track counter. In the track counter 431, n = n + 1 is set in advance as an addition formula of the variable n. At this stage, “1” is held in the variable n (steps S3 to S4). If no change is observed in the output of the hysteresis comparator 36 in step S3, the process proceeds to step S5.

  Next, the section counter comparison unit 434 obtains the current section count number from the section counter 432 and compares it with a preset reference section counter number T. As a result of the comparison, if the section count number t has not reached the reference section count number T, the process returns to step S2, and the output of the hysteresis comparator is repeatedly monitored until the reference section counter number T is reached to perform track counting. When it is detected in step S5 that the section counter t has reached the reference section counter T, the section counter comparison unit 434 outputs a comparison start signal to the track counter comparison unit 433. Here, the track counter comparison unit 433 acquires the current value of the track counter n from the track counter 431, and compares this value with the reference track count number N (step S6).

  If the track count number n is equal to or exceeds the reference track count number N as a result of the comparison, it is determined that the track servo has been applied to the signal layer, and a “track detection signal” is output to the servo control unit 44. (Step S7). On the other hand, when the track count number n does not reach the reference track count number N, it is determined that the focus servo has been applied to the cover layer, and a “track non-detection signal” is output to the servo control unit 44. As a result of this determination, when the focus servo is applied to the cover layer, the servo control unit 44 makes the focus direction and the track to the drive means 50 in order to retry the focus servo retry and the focus-related automatic adjustment at the start. A direction drive control signal is output.

  In step S6 of the determination method described above, the comparison reference is the same as or more than the reference track count number N. However, the comparison reference is not limited to this, and the track counter number n is set to 10 with respect to the reference track count number N. You may set to 1 /. With this setting, when the track counter number n is less than one-tenth of the reference track count number N, the actually measured track count number n is extremely larger than the reference track count number N (about several hundreds). Therefore, it is determined that noise has been detected, and it is determined that the focus servo has been applied to the cover layer. On the other hand, when the track counter number n is 1/10 or more of the reference track count number N, it is determined that the track has been detected, and it is determined that the focus servo has been applied to the signal layer.

  As described above, according to the configuration and the determination method of the present invention, when the eccentricity of the optical disk 10 is greater than a certain value, the number of tracks detected by the optical means 20 is about several hundreds and the noise is about several tens. Therefore, when it is detected that the track count number n is less than 1/10 of the reference track count number N measured in advance, it is determined that the focus servo is applied to the cover layer of the optical disc 10. However, if it is more than that, it can be determined that the focus servo is applied to the signal layer, so even if noise is detected in the state where the focus servo is applied to the cover layer, the noise and track can be determined. The detection accuracy of the track can be improved as compared with the prior art.

  When reading from a blue laser optical disk using Blu-ray, the eccentricity of the blue laser optical disk is normally about 30 μm to about 100 μm, and one track width of Blu-ray is 0. Therefore, the number of tracks detected when the eccentricity is 30 μm is 187 (30 μm × 2 ÷ 0.32), and the number of tracks when the eccentricity is 100 μm is 625 μm (100 μm × 2 ÷ 0. 32). Therefore, when the number of tracks is set to the reference track count N of the track counter comparison unit 433 and it is detected that the number is less than this track number or less than one tenth of this track number, It is determined that the focus servo has been applied to the cover layer. Thereby, when noise is detected in a state where focus servo is applied to the cover layer, it is possible to determine the noise and the track, so that the track detection accuracy of the blue laser optical disk can be improved.

  In addition, since this determination can be realized by providing a determination control function for detecting the number of tracks and comparison determination, no additional hardware is required, and determination processing can be performed by software processing. It is also possible.

  Next, a second embodiment according to the present invention will be described with reference to FIGS. FIG. 4 is a flowchart for explaining a determination method according to the second embodiment.

  This determination method assumes the case where the eccentricity of the optical disk 10 is not constant or the eccentricity is small, whereas the first embodiment assumes that the eccentricity of the optical disk 10 is greater than a certain value. In such a case, the present invention provides a method that can detect whether the focus servo is applied to the signal layer or the cover layer.

  In describing the present embodiment, steps S11 to S17 in the flowchart shown in FIG. 4 correspond to steps S1 to S7 described in FIG. 3, and thus detailed description of these steps is omitted.

  Therefore, description will be made from step S18 of FIG. In step S18, when the number of tracks in a predetermined measurement section is counted in steps S11 to S16 in the preceding stage, and it is detected that the counted value is less than the reference track count number N, the focus servo is applied to the cover layer of the optical disc 10. In this step, the servo control unit 44 outputs a signal for driving the tracking actuator 23 to the tracking control unit 42 when it is determined that the above has occurred.

  Here, since the optical disc 10 targeted in the present embodiment is the optical disc 10 when there is no eccentricity or the amount of eccentricity is small, even if it is determined in step S18 that the focus servo is applied to the cover layer, This is because there is little eccentricity, so that there may be a case where no pit enters the irradiated laser spot range (that is, no track extends over the laser spot range even when the tracking servo is not applied). Therefore, even if it is determined that the cover layer is once, tracking control is performed on the tracking actuator D / A 52 by notching that the drive command signal is output to the tracking control unit 42 in step S18 for reconfirmation. A signal is output to slightly swing the objective lens 21 in a direction crossing the track of the optical disk 10.

  Here, the drive voltage applied to the tracking actuator 23 will be described with reference to FIG. A graph (1) in FIG. 5 represents a cycle of one rotation of the optical disk. On the other hand, the graph (2) is a graph showing a change in voltage application to the tracking actuator 23 with respect to the rotation of the optical disk. As shown in the figure, a voltage is linearly applied to the tracking actuator 23 at a constant rate so that the trajectory is sufficiently different from the eccentricity of the optical disk 10, and the optical means 20 is unidirectional at a constant speed in the transverse direction of the track. Move to. As a result, even when there are zero tracks that pass through the laser spot range at the beginning of reproduction (in a state where only the focus servo is applied), the presence or absence of tracks can be detected in more detail by moving the optical means 20 while performing normal track detection. Can be detected. In other words, track detection is simultaneously performed by repeating steps S19 to S26 at the same time (steps S19 to S26 are the same as steps S11 to S17).

  Thus, when there is no or little eccentricity of the optical disc 10 and no track is detected, the track detection is performed while the optical means 20 is finely driven again, so that even if there is no eccentricity, it is ensured. The presence or absence of a track, that is, whether the focus servo is applied to the signal layer or the cover layer can be detected.

  Therefore, according to the determination method according to the present embodiment, the focus servo state to the cover layer can be detected regardless of the eccentricity of the optical disk. For most optical discs 10 having a certain amount of eccentricity, it is possible to detect the focus servo state to the cover layer by the first determination without finely driving the tracking actuator 23, and some eccentricity. For an optical disk with a small amount, it becomes possible to detect focus servo to the cover layer by the second determination. That is, both of the eccentric states can be handled by this determination method.

  Next, a third embodiment according to the present invention will be described with reference to FIG. FIG. 6 is a flowchart for explaining a determination method according to the third embodiment.

  This determination method is based on the assumption that the third embodiment has no eccentricity of the optical disk 10 or a small amount of eccentricity, whereas the optical disk 10 has an eccentricity. It is a determination method that can deal with various situations, and can detect whether the focus servo is applied to the signal layer or the cover layer in any situation.

  This determination method has substantially the same configuration as the configuration in which steps S11 to S17 in the previous stage are deleted from the determination method described in FIG. That is, step S30 to step S38 in FIG. 6 substantially correspond to step S18 to step S26 described in FIG.

  In step S30 in FIG. 6, the optical disk 10 is set to the spindle motor 11 to start rotation, the objective lens 21 is moved to the reading start point of the optical disk 10, and the tracking actuator 23 is moved to the position of the optical disk as shown in FIG. Drive along a trajectory that is sufficiently different from the core. At this time, for example, when the measurement interval is one rotation of the optical disc, the voltage of the tracking actuator 23 is linearly increased at a constant rate within the measurement interval, and thereafter, steps S31 to S38 are performed in the same procedure as in the first embodiment. Since the tracking actuator 23 can be finely moved in the cross direction of the track from the beginning, regardless of whether the optical disk 10 has eccentricity, the signal layer or Whether the focus servo is applied to the cover layer can be detected.

  According to such a determination method, it is possible to reliably determine the signal layer and the cover layer in the first determination regardless of the eccentricity amount of the optical disc 10 as compared with the determination method according to the second embodiment. Become. On the other hand, since the tracking actuator 23 must be driven, there is a possibility of affecting automatic adjustment performed after the focus servo determination. On the other hand, in the determination method according to the second embodiment, it is not necessary to drive the tracking actuator 23 if it can be detected that the focus servo has been applied to the signal layer in the first determination. Is possible.

1 is a block diagram showing a configuration of an optical disc device according to an embodiment of the present invention. It is a block diagram which shows the specific structure of the determination part with which the optical disk apparatus which concerns on embodiment of this invention is equipped. 6 is a flowchart for explaining a determination operation for determining a signal layer and a cover layer in the optical disc apparatus according to the embodiment of the present invention. 10 is a flowchart for explaining a determination operation for determining a signal layer and a cover layer in the optical disc apparatus according to the second embodiment of the present invention. It is a graph which shows the relationship between the eccentricity of an optical disk, and the voltage applied to a tracking actuator. It is a flowchart for demonstrating the determination operation | movement which determines a signal layer and a cover layer in the optical disk apparatus based on the 3rd Embodiment of this invention. It is a graph which shows the S-shaped curve characteristic of the focus error signal used for focus servo control. It is sectional drawing of an optical disk. It is a comparison characteristic graph of the focus error signal output when a laser beam is irradiated to two types of optical disks.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical disk 11 ... Spindle motor 20 ... Optical means 21 ... Objective lens 22 ... Focus actuator 23 ... Tracking actuator 30 ... Signal correction means 31 ... Signal calculating part 32 ... FEP
35 ... Band pass filter (BPF)
36 ... Hysteresis comparator 40 ... Calculation / control means 41 ... Focus control section 42 ... Tracking control section 43 ... Determination section 44 ... Servo control section 50 ... Drive means 53 ... Focus actuator driver 54 ... Tracking actuator driver 60 ... Sampling clock 100 ... Optical disk DESCRIPTION OF SYMBOLS 101 ... Transparent disk board | substrate 102 ... Signal layer 102a ... Signal surface 103 ... Cover layer 103a ... Cover surface 431 ... Track counter 432 ... Section counter 433 ... Track counter comparison part 434 ... Section counter comparison part

Claims (2)

An objective lens for condensing a light beam on a track on the optical disk, a light detection means for detecting at least reflected light reflected from the track on the optical disk, and an irradiation position of the light beam from the light signal detected by the light detection means An optical disc apparatus comprising at least tracking error signal generating means for calculating a positional deviation between the track and the track and generating a tracking error signal, and tracking driving means for moving the objective lens in the transverse direction of the track based on the tracking error signal Because
A signal correction means for correcting the tracking error signal if the amplitude of the tracking error signal and superimposed noise is equal to or greater than a certain threshold;
Counting means for counting the number of tracks based on the tracking error signal corrected by the signal correction means;
Storage means for storing, as a reference track number, the number of tracks detected when the optical disk is rotated for a predetermined time;
Comparing means for comparing the reference track number with the measured track number, with the number of tracks detected within a time equivalent to the fixed time as the measured track number when reading the information recorded on the optical disc;
As a result of comparison, when the number of measured tracks is less than the reference number of tracks, it is determined that a focus servo has been applied to an area where no track exists on the optical disc, and when the number of measured tracks is equal to or greater than the reference number of tracks Determination means for determining that the focus servo is applied to the area where the track of
An optical disc apparatus comprising:   When the determination means determines that the number of measured tracks is less than the reference number of tracks, the tracking drive means sends a drive signal for moving the objective lens in a specific direction at a constant speed in a direction crossing the track of the optical disk. 2. The optical disk apparatus according to claim 1, further comprising tracking control means for outputting to the optical disk.

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