JP2005092992A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive in which a tracking error signal can be switched to a DPD (Differential Phase Detection) system or a PP (Push Pull) system in accordance with change in a region to be tracked. <P>SOLUTION: When a HD (High Definition) DVD 100 which is provided with an area 101 for reproduction only in which information is formed by pits, a recordable area 2 in which information is recorded in land/groove, and a flat signal-less area 103 existing between the area for reproduction only and the recordable area is played back, tracking is performed by the DPD system in the area 101 for reproduction only, and tracking is performed by the PP system in the recordable area 102. The tracking system is switched by detecting a signal by a laser beam reflected by the signal-less area 103 included in a RF signal and thereby detecting change from the area 101 for reproduction only of the tracking area to the recordable area 102 or change from the recordable area 102 to the area 101 for reproduction only. Thus, the tracking of the HD DVD 100 can be smoothly performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc, and in particular, for example, a first area where a signal is optimally reproduced by a DPD (differential phase detection) system, a second area and a first area where a signal is optimally reproduced by a PP (push pull) system. The present invention relates to an optical disc apparatus for recording and reproducing an optical disc having a third area (mirror area) where no signal is recorded provided between the first area and the second area.

  In recent years, development of high-density optical discs that record and reproduce signals using blue-violet laser diodes has been actively promoted. In the working group 11 of the DVD Forum that promotes the standardization of optical discs, the standardization of HD (High Definition) DVD, commonly called AOD (Advanced Optical Disc) is under discussion. As shown in FIG. 5A, the HD DVD 100 can be recorded with a read-only area 101 in which signals are recorded in advance when a disc is formed, a recordable area 102 in which information is recorded by a user, and a read-only area 101. There is a non-signal area 103 formed between the area 102 and no signal recorded. As shown in FIG. 5B, disc information is recorded in the read-only area 101 by pits 101a formed by embossing. This area is also called a system lead-in area. The recordable area 102 includes a groove 102a formed in a convex shape and a land 102b formed in a concave shape. This area is also called a data area. The no-signal area 103 is formed in a flat mirror shape without unevenness, and is also called a connection area.

  The HD DVD 100 has a 1.2 mm-thick disc structure in which 0.6 mm-thick discs, the same as a DVD (Digital Versatile Disc), are bonded together, so that the existing DVD manufacturing apparatus can be used. Is taken into account. Further, since the thickness is the same as that of a DVD, it is easy to provide compatibility with a DVD and a CD (Compact Disc). The track pitch of the system lead-in area 101 is 0.68 μm, and the shortest pit length is 0.408 μm. The track pitch between lands and grooves in the data area 102 is 0.68 μm, and the distance between lands and grooves is 0.34 μm. Signal recording is performed on both the land and the groove.

  The HD DVD standard stipulates that the signal formed in the system lead-in area 101 is optimally tracked by the DPD method, and the signal formed in the data area 102 is optimally tracked by the PP method. It is stipulated. Therefore, an optical disc apparatus for recording / reproducing HD DVD needs to switch the tracking error signal between the DPD method and the PP method depending on the area to be tracked.

  Therefore, a main object of the present invention is to provide an optical disc apparatus capable of switching a tracking error signal between a DPD method and a PP method in accordance with a change in a tracking area.

  The invention of claim 1 includes a first region tracked by the DPD method, a second region tracked by the PP method, and a third region having a mirror-like surface located between the first region and the second region. An optical disc apparatus for recording / reproducing an optical disc, comprising: a detecting unit that detects a signal due to reflected light of a laser beam in a third region included in a reproduction signal; and a switching unit that switches a tracking method according to a detection result of the detecting unit. An optical disc device is provided.

  In the first aspect of the invention, the detection means detects a signal due to the reflected light of the laser beam in the third region included in the reproduction signal (RF signal), and the switching means sets the tracking method to the DPD method according to the detection result of the detection means. And switch between PP methods. Accordingly, an optical disc including a first region tracked by the DPD method, a second region tracked by the PP method, and a third region having a mirror-like surface located between the first region and the second region, for example, HD The DVD can be properly tracked.

  In the invention of claim 2, the detection means includes a bottom detection means for detecting the bottom voltage of the reproduction signal, a generation means for generating a reference voltage, and a comparison means for comparing the bottom voltage with the reference voltage. 2. The optical disk device according to claim 1, wherein the tracking method is switched when the bottom voltage is larger than the reference voltage as a result of comparison by the comparison means.

  In the invention of claim 2, the comparing means compares the bottom voltage of the reproduction signal detected by the bottom detecting means with the reference voltage generated by the generating means, and the switching means is configured to detect when the bottom voltage is larger than the reference voltage. Switch the tracking method. The bottom voltage of the reproduction signal becomes larger than the reference voltage only in the third region. In addition, when the area to be tracked is switched between the first area and the second area, the area always passes through the third area. Therefore, an optical disc such as an HD DVD can be appropriately tracked by switching the tracking method at a timing when the bottom voltage becomes larger than the reference voltage.

  According to a third aspect of the present invention, the generating means includes peak detecting means for detecting a peak voltage of the reproduction signal, and generates a reference voltage that is an average of the highest voltage and the lowest voltage of the reproduction signal in the first region. The optical disk device according to 1 or 2.

  According to a third aspect of the present invention, the generating means generates a voltage that is an average of the highest voltage and the lowest voltage of the reproduction signal in the first region as a reference voltage. Therefore, it is possible to always generate an optimum reference voltage.

  According to the present invention, the RF signal generated in the third region existing between the first region tracked by the DPD method and the second region tracked by the PP method is detected, and the tracking method is determined at the detected timing. Switch. Therefore, an optical disk such as an HD DVD having the first area, the second area, and the third area can be appropriately tracked.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  An optical disc apparatus 10 according to an embodiment of the present invention shown in FIG. 1 is loaded with an HD DVD 100 and is controlled to rotate by a spindle motor 30 that rotates in response to a signal from a spindle motor drive circuit (not shown). As described above, the HD DVD 100 includes the system lead-in area 101 in which signals are formed in advance by embossing and the data area 102 in which signals are recorded by the user. The system lead-in area 101 performs tracking by the DPD method, and the data area 102 performs tracking by the PP method. Therefore, it is necessary to switch the tracking method depending on the type of area to be tracked. When the tracking method needs to be switched because the tracking location changes from the system lead-in area 101 to the data area 102, the mirror-like connection area 103 is always passed. Therefore, in the optical disc apparatus 10 of this embodiment, when the signal crosses the connection area 103, a signal due to the reflected light of the laser beam in the connection area 103 appearing in the RF signal (reproduction signal) is detected, and the tracking method is switched by this signal. Know the timing.

  The optical disk device 10 includes an optical pickup 12. The optical pickup 12 controls the laser drive circuit (not shown) to emit laser light from the blue-violet laser diode 14. The laser light emitted from the blue-violet laser diode 14 is converted into a parallel light beam by the collimating lens 16 and passes through the beam splitter 18. The laser light that has passed through the beam splitter 18 enters the objective lens 20 and is condensed, and the condensed laser light is irradiated onto the HD DVD 100.

  At this time, a focus coil drive voltage is applied to the focus coil 22 by the focus drive circuit 36. As a result, the focus coil 22 is driven, the position of the objective lens 20 in the optical axis direction is controlled, and the laser light from the objective lens 20 is adjusted so as to be condensed on the signal surface of the HD DVD 100.

  Further, the tracking coil 24 is controlled by the tracking coil drive voltage output from the tracking drive circuit 38, and the laser light spot is controlled to follow the pit row and land / groove track on the HD DVD 100.

  The laser beam irradiated on the HD DVD 100 is reflected on the HD DVD 100, and the reflected laser beam enters the beam splitter 18 through the objective lens 20. The incident laser light is reflected by the beam splitter 18 and enters the condenser lens 26. The laser beam is condensed by the condenser lens 26 and irradiated onto the photodetector 28.

  As shown in FIG. 1, the photodetector 28 is divided into areas A, B, C, and D that are equally divided into four. Based on the laser light irradiated to each of the areas A to D, the calculation shown in the following equations (1), (2), (3), and (4) is performed. The tracking error signal (TES1) of the DPD method generates the tracking error signal (TES2) of the PP method according to Equation 3, and the focus error signal (FES) according to Equation 4. In Equations 1 to 4, symbols A to D indicate laser beams detected by the divided regions A to D of the photodetector 28, respectively. Equation 3 shows that the DPD tracking error signal is generated from the phase difference of the sum of the signals obtained from the regions located diagonally to each of the four regions A to D.

  The calculations of Equations 1 to 4 are executed by the RF signal generation circuit 42, the DPD signal generation circuit 52, the PP signal generation circuit 54, and the FE signal generation circuit 56. The PDP signal is used when tracking is performed in the system lead-in area 101, and the PP signal is used when tracking is performed in the data area 102.

  The focus error signal (FES) generated by the FE signal generation circuit 56 is input to the FE gain variable circuit 64 for gain adjustment. The focus error signal for which the gain adjustment has been performed is input to the phase compensation circuit 66 to perform phase compensation and is provided to the focus drive circuit 36. As a result, the focus coil drive voltage for driving the focus coil 22 is obtained as described above.

  The DPD tracking error signal (TES1) generated by the DPD signal generation circuit 52 and the PP tracking error signal (TES2) generated by the PP signal generation circuit 54 are respectively connected to two input terminals of the analog switch 58. Entered. The analog switch 58 switches whether to output a DPD tracking error signal or a PP tracking error signal when a tracking method selection signal (TESEL) is input from the system controller 40.

  The tracking error signal output from the analog switch 58 is input to the TE gain variable circuit 60 and gain adjustment is performed. The tracking error signal whose gain has been adjusted is input to the phase compensation circuit 62 to be phase compensated and applied to the tracking drive circuit 38. As a result, the tracking coil driving voltage for driving the tracking coil 24 is obtained as described above.

  The RF signal (reproduction signal) generated by the RF signal generation circuit 42 is input to the system controller 40, and information included in the signal is decoded.

  The RF signal is also input to the bottom detection circuit 44 and the peak detection circuit 50 in order to determine the output timing of the tracking method selection signal. The bottom detection circuit 44 is a circuit that holds the lowest voltage level of the RF signal, and the peak detection circuit 50 is a circuit that holds the highest voltage level of the RF signal. The bottom detection circuit 44 and the peak detection circuit 50 are configured by a general operational amplifier, a diode D, a hold capacitor C, a resistor R, and the like. In both the bottom detection circuit 46 and the peak detection circuit 50, the holding voltage is cleared by the control voltage supplied from the system controller 40.

  The HD DVD 100 in which no signal is recorded in the data area 102 is rotationally controlled by the spindle motor 30, and the optical pickup 12 is moved from the inner peripheral side to the outer peripheral side of the HD DVD 100 by the thread motor 34 of the thread mechanism 32 in a state where the focus servo is applied. When moving in the direction, an envelope of the RF signal as shown in FIG. 2A is obtained. Such an RF signal is supplied to the bottom detection circuit 44 and the peak detection circuit 50.

  As shown in FIG. 2A, in the system lead-in area 101, since pits are formed by embossing, a large amplitude envelope is obtained in a portion where pits exist, and in a portion where no pits exist. A small amplitude envelope is obtained. In the connection area 103, no pit or the like is formed, and since it is a plane, no RF signal component is generated. In addition, since no diffraction of light by the land / groove occurs, only a high voltage DC component is output. The data area 102 of the HD DVD 100 employs a material for the recording layer that has low reflection in an unrecorded state and high reflection in a recorded state. Accordingly, the unrecorded data area 102 has a relatively low RF signal voltage.

  Both the output voltages of the bottom detection circuit 44 and the peak detection circuit 50 are input to the system controller 40. The output voltage of the bottom detection circuit 44 is also input to the plus terminal (+) of the comparator 46. The output voltage of the reference voltage generation circuit 48 that can vary the output voltage in accordance with an instruction from the system controller 40 is input to the minus terminal (−) of the comparator 46.

  The output from the bottom detection circuit 44 input to the comparator 46 is indicated by a solid line in FIG. Such a bottom voltage and the output voltage (comparison voltage) of the reference voltage generation circuit 48 are compared by the comparator 46. The reference voltage generation circuit 48 outputs a voltage (comparison voltage) that is an average of the output voltage of the bottom detection circuit 44 and the output voltage of the peak detection circuit 50 in the system lead-in area 101 in accordance with an instruction from the system controller 40. The

  The comparator 46 compares the output of the bottom detection circuit 44 with the output of the reference voltage generation circuit 48. When the output of the bottom detection circuit 44 is large, a high level signal is output, and conversely, when the output of the bottom detection circuit 44 is small. Outputs a low level signal. Therefore, a bottom binarized signal as shown in the lower part of FIG. 2B, which is at a low level in the system lead-in area 101 and the data area 102 and is at a high level only in the connection area 103, is obtained.

  When the optical pickup 12 is moved from the outer peripheral side toward the inner peripheral side, a voltage as shown in FIG. 2C is output from the bottom detection circuit 44. The output from the bottom detection circuit 44 and the comparison voltage from the reference voltage generation circuit 48 are compared by the comparator 46, whereby a bottom binarized signal as shown in the lower part of FIG. The bottom binarized signal in this case is also at a low level in the system lead-in area 101 and the data area 102 and is at a high level only in the connection area 103.

  In the case of the HD DVD 100 in which a signal is recorded in the data area 102, when the optical pickup 12 is moved from the inner peripheral side to the outer peripheral side of the HD DVD 100 with the focus servo applied, FIG. An envelope as shown is obtained. As can be seen from FIG. 3A, since the laser light is diffracted by the signals written in the land and groove, a high RF signal component is obtained in the data area 102.

  However, as can be seen from FIG. 3B, the bottom voltage output from the bottom detection circuit 44 is lower than the comparison voltage in the system lead-in area 101 and the data area 102, and is lower than the comparison voltage only in the connection area 103. It is high. Therefore, the bottom binarized signal obtained in this case is at a low level in the system lead-in area 101 and the data area 102 and is at a high level only in the connection area 103.

  Further, when the optical pickup 12 is moved from the outer peripheral side to the inner peripheral side of the HD DVD 100, as can be seen from FIG. 3C, as in the other cases described above, the system lead-in area 101 and A bottom binarized signal that is at a low level in the data area 102 and is at a high level only in the connection area 103 is obtained.

  Such a bottom binarization signal is supplied to the system controller 40. The system controller 40 generates a tracking method selection signal at the timing when the bottom binarization signal changes from the low level to the high level, and supplies the tracking method selection signal to the analog switch 58.

  The analog switch 58 switches the output signal from the DPD tracking error signal to the PP tracking error signal or from the PP tracking error signal to the DPD tracking error signal when the tracking method selection signal is given. The analog switch 58 does not consider whether the output is a DPD tracking error signal or a PP tracking error signal. Since the HD DVD 100 always starts playback from the system lead-in area 101, it is set to select a DPD tracking error signal first, and thereafter, every time the optical pickup 12 crosses the connection area 103, that is, tracking. The polarity of the switch may be switched every time a method selection signal is given.

  The operation of the system controller will be described below using the flowchart shown in FIG. When the HD DVD 100 is mounted on the optical disc apparatus 10, the rotation of the HD DVD 100 is controlled by the spindle motor 30. When the HD DVD 100 is mounted on the optical disc apparatus 10, the system lead-in area 101 that is tracked by the DPD tracking error signal is reproduced. First, in step S1, the system controller 40 sets the polarity of the analog switch 58 to the DPD method. Set to the side that outputs the tracking error signal.

  Next, the sled motor 34 is driven to send the optical pickup 12 to the system lead-in area 101 to perform focus servo. At this time, the RF signal reproduced by the RF signal reproduction circuit 42 is supplied to the bottom detection circuit 44 and the peak detection circuit 50. An average voltage between the highest voltage of the RF signal output from the bottom detection circuit 44 and the lowest voltage of the RF signal output from the peak detection circuit 50 is calculated. The reference voltage generation circuit 48 is controlled so as to generate this average voltage. The average voltage output from the reference voltage generation circuit 48 and the output from the bottom detection circuit 44 are input to the respective input terminals of the comparator 46, so that preparation for generating the bottom binarized signal is completed.

  After the disc information is reproduced from the system lead-in area 101, when an access is made to the target address by thread operation or tracking control, the RF signal due to the reflection of the laser beam in the connection area 103 when passing through the connection area 103 Is detected by comparing the bottom voltage with the comparison voltage, and the bottom binarized signal changes from the low level to the high level. This change in signal from the low level to the high level is detected in step S3, and in step S5, the tracking system selection signal is output and the polarity of the analog switch 58 is switched to select the PP tracking error signal. Set.

  Thereafter, every time the bottom binarization signal becomes high level, the tracking method selection signal is output to switch the polarity of the analog switch 58. Then, when a stop button (not shown) of the optical disk device 10 is operated or a power button (not shown) is operated, this is detected in step S7 and the process is terminated.

  As described above, in the optical disc apparatus 10 of this embodiment, the RF signal in the connection area 103 located between the system lead-in area 101 tracked by the DPD method and the data area 102 tracked by the PP method is received. When detected, the tracking method is switched between the DPD method and the PP method. Since the tracking area always crosses the connection area 103 when the system lead-in area 101 and the data area 102 are switched, the HD DVD 100 is appropriately switched by switching the tracking method at the timing when the signal in the connection area 103 is detected from the RF signal. Can be tracked.

It is an illustration figure which shows the whole structure of one Example of this invention. It is an illustration figure which shows RF signal in an unrecorded HD DVD, a bottom detection circuit output signal, and a tracking system selection signal. It is an illustration figure which shows RF signal in a recorded HD DVD, a bottom detection circuit output signal, and a tracking system selection signal. It is a flowchart which shows operation | movement of the system controller in the Example of FIG. It is an illustration figure which shows schematic structure of HD DVD.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical disk system 12 ... Optical pick-up 40 ... System controller 42 ... RF signal reproduction circuit 44 ... Bottom detection circuit 46 ... Comparator 48 ... Reference voltage generation circuit 50 ... Peak detection circuit 52 ... DPD signal detection circuit 54 ... PP signal detection circuit 58 … Analog switch 100… HD DVD
101 ... System lead-in area 102 ... Data area 103 ... Connection area

Claims (3)

Optical disc apparatus for recording / reproducing an optical disc including a first region tracked by the DPD method, a second region tracked by the PP method, and a third region having a mirror-like surface located between the first region and the second region Because
An optical disc apparatus comprising: detection means for detecting a signal due to reflected light of laser light in the third region included in a reproduction signal; and switching means for switching a tracking method according to a detection result of the detection means. The detecting means includes bottom detecting means for detecting a bottom voltage of the reproduction signal, generating means for generating a reference voltage, and comparing means for comparing the bottom voltage with the reference voltage,
2. The optical disc apparatus according to claim 1, wherein the switching unit switches the tracking method when the bottom voltage is larger than the reference voltage as a result of the comparison by the comparison unit.   The said generation | occurrence | production means contains the peak detection means to detect the peak voltage of the said reproduction | regeneration signal, The reference voltage used as the average of the highest voltage of the said reproduction | regeneration signal in the 1st area | region and the minimum voltage is generated. Optical disk device.

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