JP2005235299A - Device for detecting moving direction of objective lens and tracking control apparatus having same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for detecting the moving direction of an objective lens, which can precisely detect the moving direction of the objective lens and which can realize a stable and high-speed pull-in operation into the tracking control after the seek, even for an optical disk in an unrecorded state or in the state in which the unrecorded state and a recorded state are mixed. <P>SOLUTION: The device, which has RF signal output circuits (21, 23 and 25) for outputting an RF detection signal, wobble signal generation circuits (31, 32 and 33) for generating a wobble detection signal, tracking error signal generation circuits (34 and 35) for generating a tracking error signal, and a record existence/absence detection circuit 24 for detecting whether an area on the disk is a recorded area or an unrecorded area, on the basis of the RF signal, detects the moving direction of the objective lens on the basis of the RF detection signal and the tracking error signal when the detection result of the record existence/absence detection circuit 24 results in the recorded area, or detects the moving direction of the objective lens on the basis of the wobble detection signal and the tracking error signal when the detection result results in the unrecorded area (41, 42 and 43). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an objective lens movement direction detection device that detects a movement direction of an objective lens provided in an optical pickup or the like of an optical disk device in the radial direction of the optical disk. The present invention also relates to a tracking control device having the objective lens movement direction detection device.

  In an optical disc apparatus for recording and reproducing information on an optical disc such as a DVD-R (Digital Versatile Disk Recordable), DVD-RW / DVD + RW (Digital Versatile Disk ReWritable), DVD-RAM (Digital Versatile Disk Random Access Memory) By irradiating the information recording surface of the optical disc with the emitted light emitted from the light source, information such as music is written on the optical disc, and the reflected light returned from the information recording surface of the optical disc is detected. To read (reproduce) information. An optical pickup is used for recording and reproducing this information.

  An optical pickup is a semiconductor laser as a light source, an optical system with an objective lens that focuses the light emitted from the light source and collects the reflected light from the optical disk, and converts the optical signal into an electrical signal. In this optical pickup, in order to reliably write information on the optical disc or read information from the optical disc, the emitted light from the optical pickup is always on the recording position of the optical disc. Is controlled so as to move the objective lens in the radial direction of the optical disc (hereinafter referred to as “tracking (servo) control”).

  As a tracking control method, for example, the one shown in FIG. 7 is known. FIG. 7D is a cross-sectional view in which the surface of the optical disk is cut in the disk radial direction. The protrusion L is called a land, and the recess G is called a groove. A track (recording track) is formed in advance by a land L or a groove G on an information recording surface of a recording type (or write-once type) optical disc such as a DVD-R or a DVD-RW. Information is recorded by irradiating the emitted laser beam.

  In the following description, it is assumed that information is written in the groove G. Here, when the optical pickup provided with the objective lens is moved in the radial direction of the disk (left and right direction in FIG. 7), the emitted light from the optical pickup moves so as to cross the land L and the groove G.

  During this movement, the RF signal detected by the photodetector (photodetector) that receives the reflected light from the optical disk is as shown in FIG. When this RF signal is envelope-detected, an RF detection signal as shown in FIG. 7B is obtained. In the RF detection signal, the center of the waveform peak matches the center position of the land L, and the center of the waveform valley matches the center position of the groove G, as shown in FIG.

  Further, a tracking error signal as shown in FIG. 7C can be obtained by performing a predetermined matrix calculation on the light detection signal detected by the light detector (light detector). In the tracking error signal, the waveform passes through the zero level B at a position corresponding to the center position of the groove G (hereinafter referred to as “zero crossing”).

  Therefore, when information is recorded and reproduced in the groove G sandwiched between the two lands L in FIG. 7, first, the slope of the tracking error signal (ie, the RF detection signal indicates the center C of the predetermined valley) The optical pickup is moved in the disk radial direction based on the differential coefficient. This operation is called “tracking (servo) control”. After that, tracking control is performed by performing position control so that the tracking error signal crosses zero.

  Further, as shown in FIG. 7D, the optical disc apparatus can detect the land L and groove G of the optical disc using the tracking error signal and the RF detection signal, and the RF detection signal is detected by the tracking error signal and the disc. Using the fact that there is a phase difference of 90 degrees in the radial direction, the moving direction of the objective lens in the radial direction on the optical disc (the moving direction of the objective lens relative to the radial direction of the optical disc, hereinafter simply referred to as “moving direction”) (The detection signal may be referred to as a “movement direction detection signal” hereinafter).

  In addition to the tracking control described above, the optical pickup control includes seek control for moving the light beam to a desired track. After switching from the seek control mode to the tracking control mode, at the time of pulling in the tracking control. When the light beam spot crosses the track, the movement of the objective lens is braked based on the radial movement direction of the objective lens on the optical disk. As a result, the tracking control after seeking is performed quickly and stably.

  However, recording type (or write-once type) optical discs such as DVD-R and DVD-RW are generally shipped to the market in a state where information is not recorded. Therefore, when recording is performed on a track in an unrecorded area of the optical disc, Since the information is not recorded, the RF detection signal cannot be generated (it can be said that “the RF detection signal cannot be generated because the RF signal is not recorded”). Then, there is a problem that the moving direction cannot be detected, and the above-described stabilization and speeding up of the tracking control cannot be realized.

  In order to solve this problem, as another conventional configuration example, a tracking error signal and wobble detection are performed in a tracking control device for a disk-shaped recording medium in which a groove or land track is wobbled at a single frequency or a frequency close thereto. A moving direction detecting means for detecting a moving direction using a signal, and a head scanning position when the head scanning position is detected to cross the track based on the moving direction detection result after switching from a seek operation to a tracking operation. A tracking control device having a mute attenuating means for muting or attenuating a driving voltage in the moving direction for moving in the disk radial direction is disclosed (for example, see Patent Document 1 below).

  As another conventional configuration example, an optical pickup direction detection device that generates a movement direction detection signal based on a prepit signal generated from a land prepit provided on an optical disc and a tracking error signal is disclosed (for example, , See Patent Document 2 below).

As another conventional configuration example, it is detected whether the seek destination or the middle of the seek is a recording area or an unrecorded area. When the recording area is detected, a tracking error signal and a predetermined phase difference with respect to the tracking error signal are detected. A seek control method is disclosed in which the number of tracks traversed by the head during a seek operation is counted using both of the signals having, and the count is performed using only a tracking error signal when it is detected as an unrecorded area ( For example, see Patent Document 3 below).
JP 2001-202635 A JP 2000-276737 A JP 2000-331353 A

  As described above, in the conventional configuration, the moving direction cannot be detected in an unrecorded area. As a result, stable tracking control cannot be drawn.

  Further, as in the conventional configuration example described in Patent Document 1, when the moving direction is detected by using a tracking error signal and a wobble detection signal for an unrecorded state or an optical disc in which an unrecorded state and a recorded state are mixed, Especially when the RF signal frequency and the wobble frequency are close to each other, the recorded RF signal leaks into the wobble signal, the S / N ratio of the wobble signal is deteriorated, and the detection accuracy of the wobble signal is deteriorated. The moving direction cannot be detected.

  Further, in the conventional configuration example described in Patent Document 2, the movement direction cannot be detected unless the land pre-pits are provided in advance on the optical disc.

  Further, the conventional configuration example described in Patent Document 3 is intended to stably measure the number of traversed tracks when performing a seek operation on an optical disc in which a recorded state and an unrecorded state are mixed. Thus, the moving direction cannot be detected.

  In view of the above points, the present invention can accurately detect the moving direction of an objective lens even for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded state and a recorded state are mixed. An object of the present invention is to provide an objective lens movement direction detecting device that can realize stabilization and speeding-up of tracking control after seek.

  In addition, the present invention can accurately detect the moving direction of the objective lens even for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded state and a recorded state are mixed. It is an object of the present invention to provide a tracking control device capable of stabilizing and speeding up the pull-in to tracking control.

In order to achieve the above object, an objective lens movement direction detecting device according to the present invention comprises a land and a groove formed concentrically or spirally to form a track for recording information, and the side wall of the track. The objective lens that focuses the light emitted from the light source and collects the reflected light from the disk-shaped recording medium on the disk-shaped recording medium on which the wobble is formed is moved in the radial direction of the disk-shaped recording medium. In the objective lens movement direction detecting device for detecting, an RF signal generating means for generating an RF signal obtained by reproducing information recorded on the track, a wobble signal generating means for generating a wobble signal corresponding to the wobble,
Tracking error signal generating means for generating a tracking error signal used for tracking control for causing the objective lens to follow the track, and an area on the disc-shaped recording medium on which the emitted light is imaged are recorded with information. Recording presence / absence detection means for detecting whether the recording area is an unrecorded area where information is not recorded or not based on the RF signal, and the detection result of the recording presence / absence detection means is recorded in the recording area. In some cases, the moving direction is detected based on the RF signal and the tracking error signal, and when the detection result is an unrecorded area, the moving direction is detected based on the wobble signal and the tracking error signal.

  As a result, the moving direction of the objective lens can be accurately detected even for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded status and a recorded status are mixed, and tracking control after seek is performed. It is possible to stabilize the pull-in and speed-up. In addition, the increase in speed makes it possible to reduce the power consumption of the objective lens moving direction detection device, the tracking control device including the same, and the entire optical disk device.

  In addition, for example, in the above configuration, after the seek control for moving the objective lens to a predetermined track, the recording lens detection unit further includes a search unit that performs the tracking control. Sometimes, it is detected whether the area on the disc-shaped recording medium on which the emitted light is imaged is a recording area where information is recorded or an unrecorded area where information is not recorded The objective lens movement direction detection device may be configured to detect a movement direction of the objective lens when the search means is operating.

  This makes it possible to pull in to stable tracking control after seek control at high speed.

  In order to achieve the above object, an objective lens moving direction detection device according to the present invention has a land and a groove formed concentrically or spirally to form a track for recording information, and the track The objective lens that focuses the light emitted from the light source and collects the reflected light from the disk-shaped recording medium on the disk-shaped recording medium having a wobble formed on the side wall of the disk-shaped recording medium in the radial direction An objective lens movement direction detecting device for detecting a direction, comprising: an automatic gain control circuit that outputs a control voltage so that an amplitude of an RF signal obtained by reproducing information recorded on the track is constant; RF signal generation means for generating, wobble signal generation means for generating a wobble signal corresponding to the wobble, and the objective lens Tracking error signal generating means for generating a tracking error signal used for tracking control to follow the disk and an area on the disc-shaped recording medium on which the emitted light is imaged are recording areas on which information is recorded. Or a recording presence / absence detecting means for detecting whether the information is unrecorded area based on the control voltage, and when the detection result of the recording presence / absence detecting means is a recording area, the control The moving direction is detected based on the voltage and the tracking error signal, and when the detection result is an unrecorded area, the moving direction is detected based on the wobble signal and the tracking error signal.

  As a result, the movement direction of the objective lens can be detected more accurately even for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded state and a recorded state are mixed, and tracking control after seek is performed. It is possible to achieve further stabilization and speeding-up of the drawing. In addition, the increase in speed makes it possible to reduce the power consumption of the objective lens moving direction detection device, the tracking control device including the same, and the entire optical disk device.

  The tracking control device according to the present invention includes an objective lens movement direction detection device having the above-described configuration, a frequency measurement unit that measures the frequency of the tracking error signal, and the objective lens movement when the frequency is smaller than a predetermined frequency. Brake processing means for applying a brake to the objective lens moving in the radial direction of the disc-shaped recording medium based on the moving direction detected by the direction detecting device.

  The tracking control device can be pulled into stable tracking control even when the eccentric acceleration increases.

  As described above, according to the objective lens moving direction detection device of the present invention, the objective lens can be accurately used for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded state and a recorded state are mixed. The moving direction can be detected. By using this detection result, it is possible to achieve stabilization and speeding-up of tracking control after seek.

  Further, according to the tracking control device of the present invention, the moving direction of the objective lens is accurately detected even for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded status and a recorded status are mixed. In addition, stabilization and speeding-up of tracking control after seek can be realized.

<< First Embodiment >>
Hereinafter, a first embodiment of an objective lens movement direction detection apparatus and a tracking control apparatus having the objective lens movement direction detection apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an outline of an optical disc apparatus 1 capable of recording and reproducing information such as music on a DVD-R, DVD-RW, or the like.

(Fig. 1: Outline of optical disk device)
In FIG. 1, an optical disc 2 has land and grooves formed concentrically or spirally, such as DVD-R, DVD-RW / DVD + RW, DVD-RAM, etc., for recording information such as music. In which wobbles (grooves or lands are wobbled at a single frequency or a frequency in the vicinity thereof) are formed on the side walls of the recording tracks. In DVD-R, DVD-RW, etc., information can be recorded in either a land or a groove. In DVD-RAM, etc., information can be recorded in both a land and a groove. It has become. In the following description, information such as music is recorded in the groove (information is recorded) unless otherwise specified.

  The optical disk 2 is fixed by a chucking mechanism (not shown) provided in the spindle motor 15 and is rotationally driven by the spindle motor 15 that receives the spindle drive signal from the motor driver 14. Further, the motor driver 14 includes an FG pulse (spindle rotation signal) generation circuit for detecting the rotation of the spindle motor 15, and the generated FG pulse is given to a signal processing circuit 9 described later.

  The optical pickup 3 includes a tracking actuator 4 and a focus actuator 5 that are driven by receiving a tracking drive signal and a focus drive signal supplied by a PWM driver 13 to be described later, and a semiconductor laser (light source) (not shown) and the semiconductor laser, respectively. Laser light emission control (pulse generation at the time of pulse light emission and laser power control) and collimator lens, and the light emitted from the semiconductor laser is imaged on the recording portion (track) of the optical disc 2 and from the optical disc 2 The objective lens 17 that collects the reflected light is provided.

  The objective lens 17 is driven by the focus actuator 5 (focus control is performed) so that the laser beam as the emitted light is focused on a track (for example, a groove) of the optical disc 2, and a light beam spot of the laser beam. Is driven by the tracking actuator 4 (tracking control is performed) so as to track a track (for example, a groove).

  In the case of recording information, the optical pickup 3 writes information on the track of the optical disc 2 by changing the laser emission intensity in accordance with the recording information. At this time, high-density recording is possible by emitting emitted light in pulses.

  The optical pickup 3 can be moved in the radial direction of the optical disk 2 by an intermediate transmission mechanism (not shown) such as a stepping motor that converts the rotational drive of the sled motor 6 into linear drive. The thread motor 6 is driven by a thread drive signal from the motor driver 14.

  Furthermore, the optical pickup 3 is provided with two photodetectors (not shown) for detecting reflected light. One photodetector is for detecting an RF (Radio Frequency) signal which is a main signal, and the other photodetector is a tracking error signal used for tracking control, a focus error signal used for focus control, and an optical disc. 2 is used to detect a wobble signal corresponding to the shape of the wobble above 2. Information such as music recorded on the optical disc 2 is converted into a photodetection signal (current signal) by both photodetectors and then applied to an RF processing circuit 7 to be described later and converted into a voltage signal (IV conversion). )

  The light detection signal corresponding to the main signal (information such as music) sent to the RF processing circuit 7 is composed of two signals whose phases are opposite (180 ° different), and the two signals are received by the RF processing circuit 7. A difference signal (substantially the sum signal since the phase is opposite) is obtained, and then AGC (Automatic Gain Control) processing is performed. Further, it is sent to a signal processing circuit 9 to be described later and subjected to error correction, deinterleaving, NRZI (Non Return to Zero Inverted) conversion, Viterbi decoding, and the like.

  On the other hand, the tracking error signal and the focus error signal created by the RF processing circuit 7 from the photodetection signal corresponding to the tracking error signal or the like are converted into digital signals after AD (analog-digital) conversion by an A / D converter (not shown). The signal is equalized by a phase compensation circuit (not shown) provided in the servo processing circuit 10 and further subjected to pulse width modulation (PWM) by the PWM signal generation circuit 11 and then given to the PWM driver 13. It is done. The PWM driver 13 generates the tracking drive signal and the focus drive signal described above based on the given signal, and supplies them to the tracking actuator 4 and the focus actuator 5, respectively. The digital servo processing circuit 10 is mainly composed of a digital signal processor (DSP).

  The RF processing circuit 7 also generates a wobble signal. The wobble signal is detected and sent to the signal processing circuit 9. Implementation of detection of the moving direction of the objective lens 17 in the radial direction of the optical disc 2 using the detection signal (the moving direction of the objective lens 17 relative to the radial direction of the optical disc 2; the moving direction) will be described later. The wobble signal includes address information of the optical disc 2, and the address information is also used as information when searching for a recording location of desired recording information (information such as music).

  The spin error signal generated by the signal processing circuit 9 based on the synchronization signal (frame synchronization signal) obtained from the RF signal is equalized (equalized) by the digital servo circuit 10 and then the PDM signal generation circuit 12. To be subjected to pulse density modulation (PDM). The rotation of the spindle motor 15 is controlled by supplying the modulated signal to the motor driver 14.

  The system controller 16 controls the entire optical disc 1 while controlling the signal processing circuit 9, the digital servo processing circuit 10 and the like as necessary.

(Figure 2: Description of the main part)
FIG. 2 is a block diagram showing detailed configurations of the RF processing circuit 7, the signal processing circuit 9, and the digital servo processing circuit 10 in FIG. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  The RF processing circuit 7 amplifies a signal corresponding to recording information such as music detected by the optical pickup 3 to generate an RF signal (reproduced RF signal), and a necessary band of the RF signal. An RF detection bandpass filter (BPF) 23 that extracts only the signal of, an amplitude detection circuit 25 that detects the amplitude of the signal from the RF detection bandpass filter 23, and the amplitude of the RF signal output from the RF amplifier 21 are constant. The AGC 22 that controls the gain of the RF amplifier 21 and the recording presence / absence detection circuit 24 that inputs the RF signal to determine the recording or non-recording state of the optical disc 2 and outputs a recording presence / absence signal. The signal output from the amplitude detection circuit 25 corresponds to a signal obtained by envelope detection of the reproduced RF signal (this signal is referred to as “RF detection signal”). Note that, instead of envelope detection, an RF detection signal may be obtained using a low-pass filter.

  When the area where the light beam spot of the optical disk 2 is imaged is an area where information such as music is recorded, it is input to the recording presence / absence detection circuit 24 by the operation of the RF amplifier 21 controlled by the AGC 22. The amplitude of the RF signal becomes larger than the reference value set in the recording presence / absence detection circuit 24. In this case, the recording presence / absence detection circuit 24 determines that the portion is a recording area, and outputs a recording presence / absence signal corresponding to the determination (this signal is hereinafter referred to as a “recorded signal”). On the other hand, when the region where the light beam spot of the optical disc 2 is focused is a region where information such as music is not recorded, the recording presence / absence detection circuit 24 is also operated by the operation of the RF amplifier 21 controlled by the AGC 22. The amplitude of the RF signal input to is not larger than the reference value set in the recording presence / absence detection circuit 24. In this case, the recording presence / absence detection circuit 24 determines that the portion is an unrecorded area, and outputs a recording presence / absence signal corresponding to the determination (this signal is hereinafter referred to as “no recording signal”).

  Further, the RF processing circuit 7 is a matrix amplifier 29 that performs a predetermined matrix operation on the light detection signal detected by the light detector (provided in the optical pickup 3 as described above) corresponding to the generation of the tracking error signal and the like. A focus error signal generation circuit 30, a wobble signal generation circuit 31, a tracking error signal generation circuit 34 that generate and output a focus error signal, a wobble signal, and a tracking error signal in response to the output of the matrix amplifier 29, and A wobble detection bandpass filter (BPF) 32 for extracting only a signal in a necessary band from the wobble signal, an amplitude detection circuit 33 for detecting the amplitude of the signal from the wobble detection bandpass filter 32, and a binary tracking error signal. The binarized signal (hereinafter referred to as “track”) The D flip-flop 43 which will be described later Nguera of binary signal ") and a binarization circuit 35 to provide a clock.

  The signal output from the amplitude detection circuit 33 corresponds to a signal obtained by envelope detection of a wobble signal (this signal is referred to as “wobble detection signal”). Note that, instead of envelope detection, a wobble detection signal may be obtained using a low-pass filter. The focus error signal is sent to the digital servo processing circuit 10.

  The signal processing circuit 9 receives the RF detection signal and the wobble detection signal output from the amplitude detection circuits 25 and 33, respectively, and selects one of the detection signals corresponding to the recording presence / absence signal from the recording presence / absence detection circuit 24. A switch circuit 41 applied to the binarization circuit 42, a binarization circuit 42 for binarizing the received detection signal, and a signal from the binarization circuit 42 are input to the D terminal, and the objective lens is input from the Q terminal. And a positive edge trigger type D flip-flop 43 that outputs a signal (movement direction detection signal) indicating a moving direction in the radial direction of the 17 optical disks 2.

  Specifically, the switch circuit 41 selects an RF detection signal when receiving a “recorded signal” from the recording presence / absence detection circuit 24, and selects a wobble detection signal when receiving a “no recording signal” from the recording presence / absence detection circuit 24. To the binarization circuit 42.

  The digital servo processing circuit 10 performs phase compensation of the tracking error signal and sends a tracking error signal after the phase compensation (hereinafter referred to as “tracking error phase compensation signal”) to the brake processing circuit 45, and tracking The brake control circuit 45 that receives the error phase compensation signal, the moving direction detection signal, and the output of the frequency measurement circuit 46 and outputs the brake signal to the PWM signal generation circuit 11, measures the frequency of the tracking error signal, and brakes the measurement result And a frequency measurement circuit 46 provided to the control circuit 45.

(FIG. 3, FIG. 4: Explanation of a moving direction detection signal)
Generation of the movement direction detection signal and generation of a brake signal using the movement direction detection signal will be described with reference to FIGS. 3 and 4. FIG. 3 shows signal voltage waveforms when the recording presence / absence detection circuit 24 outputs a “recording presence / absence signal” as a recording presence / absence signal. FIG. Each signal voltage waveform in the case of outputting “no recording signal” as the presence / absence signal is shown.

  First, FIG. 3 will be described. In FIG. 3, from the top, an RF signal (reproduced RF signal) generated by the RF amplifier 21, an RF detection signal obtained by envelope detection of the RF signal, a tracking error signal, and an RF detection signal are input to the binarization circuit 42 and are binarized. FIG. 7 shows voltage waveforms of the digitized RF detection binarized signal, the tracking error binarized signal output from the binarizing circuit 35, the moving direction detection signal, the tracking error phase compensation signal, and the brake signal.

  In FIG. 3, the RF detection signal is input to the binarization circuit 42. As shown in FIG. 3, the RF detection binarization signal is when the RF detection signal is greater than 0 V (such as between points P1 to P3). Becomes high level (Hi), and when it is small (between points P3 and P5, etc.), it becomes low level (Lo). Similarly, the tracking error binarized signal becomes high level (Hi) when the tracking error signal is larger than 0V (such as between points P4 to P6) and low when it is small (such as between points P2 and P4). Level (Lo). Note that the center of the peak (such as point P2) of the RF detection signal waveform matches the center position of the land, and the center of the valley (point P4 etc.) of the RF detection signal waveform matches the center position of the groove. This is the same as described with reference to FIG.

  As described above, since the tracking error binarization signal is supplied to the clock terminal of the positive edge trigger type D flip-flop 43, RF detection at the rising edge of the tracking error binarization signal (points P4, P7, etc.). The binarized signal is latched as a movement direction detection signal.

  It is detected that the moving direction is opposite between the points P1 to P6 in FIG. 3 and on the right side in the figure from the point P7. This is because the RF signal and the tracking error signal have a phase difference of 90 degrees in the radial direction of the optical disc 2 as described in the background art section.

  For example, in FIG. 3, when the movement direction detection signal is at a low level, it can be seen that the movement direction is toward the outer periphery (the direction from the inner periphery to the outer periphery of the optical disk). It can be seen that (the direction from the outer periphery to the inner periphery of the optical disk). Hereinafter, description will be made assuming that the moving direction is toward the outer circumference and the inner circumference when the movement direction detection signal is at the low level and the high level as described above (the same applies to FIG. 4).

  Since the tracking error phase compensation signal is obtained by applying phase compensation to the tracking error signal, when the tracking error signal is 0 V (the phase is 0 ° or 180 °, as can be seen from comparison between both at the point P2 in FIG. 3). ), The voltage is not 0 V (the phase is not 0 ° or 180 °).

  The brake signal voltage larger than the reference voltage Vref corresponds to a drive voltage (outer circumferential direction drive voltage) for moving the objective lens 17 from the inner circumference side to the outer circumference direction of the optical disc 2, and the brake signal voltage smaller than the reference voltage Vref is This corresponds to a driving voltage (inner circumferential direction driving voltage) for moving the objective lens 17 in the inner circumferential direction from the outer circumferential side of the optical disc 2.

  As shown in FIG. 3, when the movement direction detection signal is at a low level (the movement direction is toward the outer periphery), when the tracking error phase compensation signal is smaller than 0 V, the brake signal voltage becomes the inner periphery direction drive voltage ( Smaller than the reference voltage Vref). That is, the brake is applied to the objective lens 17 moving toward the outer periphery.

  On the other hand, when the movement direction detection signal is at a high level (the movement direction is the inner circumference), when the tracking error phase compensation signal is greater than 0 V, the brake signal voltage becomes the outer circumference drive voltage (greater than the reference voltage Vref). ). That is, the brake is applied to the objective lens 17 moving in the inner circumferential direction. When the brake is applied, the relative moving speed of the objective lens 17 in the radial direction of the optical disk 2 is attenuated, and the tracking servo is turned on.

  Next, FIG. 4 will be described. In FIG. 4, the wobble signal generated by the wobble signal generation circuit 31, the wobble detection signal obtained by envelope detection of the wobble signal, the tracking error signal, and the wobble detection signal are input to the binarization circuit 42 and binarized from above. The wobble detection binarization signal, the tracking error binarization signal output from the binarization circuit 35, the moving direction detection signal, the tracking error phase compensation signal, and the voltage waveform of the brake signal are shown.

  In FIG. 4, the wobble detection signal is input to the binarization circuit 42. As shown in FIG. 4, the wobble detection binarization signal is when the wobble detection signal is greater than 0V (such as between points S1 to S3). Becomes high level (Hi), and when it is small (between points S3 to S5, etc.), it becomes low level (Lo). Similarly, the tracking error detection binarized signal is at a high level (Hi) when the tracking error signal is also greater than 0 V (such as between points S4 to S6) and low when it is small (such as between points S2 and S4). Level (Lo). Note that the center of the peak of the wobble detection signal waveform (such as point S2) matches the center position of the land, and the center of the valley of the wobble detection signal waveform (such as point S4) matches the center position of the groove.

  As described above, since the tracking error binarization signal is supplied to the clock terminal of the positive edge trigger type D flip-flop 43, wobble detection at the rising edge of the tracking error binarization signal (eg, points S4 and S7). The binarized signal is latched as a movement direction detection signal.

  It can be detected that the movement direction is opposite between the points S1 to S6 in FIG. 4 and on the right side in the figure from the point S7. This is because the fact that the wobble signal and the tracking error signal have a phase difference of 90 degrees in the radial direction of the optical disc 2 is used.

  Therefore, in FIG. 4, when the movement direction detection signal is at a low level, it can be seen that the movement direction is toward the outer periphery (the direction from the inner periphery to the outer periphery of the optical disk). It can be seen that (the direction from the outer periphery to the inner periphery of the optical disk).

  As shown in FIG. 4, when the movement direction detection signal is at a low level (the movement direction is toward the outer periphery), when the tracking error phase compensation signal is smaller than 0 V, the brake signal voltage becomes the inner periphery direction drive voltage. That is, the brake is applied to the objective lens 17 moving toward the outer periphery.

  On the other hand, when the moving direction detection signal is at a high level (the moving direction is toward the inner circumference), when the tracking error phase compensation signal is greater than 0V, the voltage of the brake signal becomes the outer peripheral driving voltage. That is, the brake is applied to the objective lens 17 moving in the inner circumferential direction. When the brake is applied, the relative movement speed of the objective lens 17 in the radial direction of the optical disk 2 is attenuated, and the tracking servo is turned on when the frequency reaches a specified frequency (depending on the servo band) at which the tracking servo can be drawn.

  In this way, in the recording area, the moving direction is detected by the RF detection signal and the tracking error signal, and in the unrecorded area, the moving direction is detected by the wobble detection signal and the tracking error signal. Therefore, it is possible to pull in to stable tracking control after seek control at high speed.

(Figure 5: Mask for movement direction detection)
Next, the operation of the frequency measurement circuit 46 in FIG. 2 will be described with reference to FIG. FIG. 5 is a diagram illustrating voltage waveforms of the tracking error signal and the moving direction detection signal when the eccentric acceleration fluctuates. FIG. 5 shows voltage waveforms of the tracking error signal and the movement direction detection signal from above.

  The frequency measurement circuit 46 compares the frequency of the tracking error signal input to the frequency measurement circuit 46 with a reference frequency (not shown) stored by itself. When the tracking error frequency is lower than the reference frequency (points T1 to T2, T3 to T4, etc. in FIG. 5; movement direction detection is effective), the frequency is set so as to output a brake signal as shown in FIGS. The measurement circuit 46 controls the brake control circuit 45. On the other hand, when the tracking error frequency is higher than the reference frequency (points T2 to T3, etc. in FIG. 5), the movement direction detection signal output from the D flip flip 43 is not accurate, and the brakes as shown in FIGS. The frequency measuring circuit 46 controls the brake control circuit 45 so as not to output a signal.

  When the eccentric acceleration increases, the frequencies of the tracking error signal, the RF detection signal, and the wobble detection signal increase. Then, it is included in the detection circuit (RF detection BPF 23, amplitude detection circuit 25, wobble detection BPF 32, amplitude detection circuit 33) provided for improving the S / N ratio of each of the RF detection signal and the wobble detection signal. The phase delay caused by the filter hinders accurate movement direction detection. At points T2 to T3 in FIG. 5, although the moving direction detection signal is correct that the high level (Hi) is constant, it is a low level (Lo) signal because the eccentric acceleration is large. (That is, an erroneous movement direction detection signal).

  If it is assumed that the moving direction detection signal is valid (accurate) at points T2 to T3 in FIG. 5 and the brake control circuit 45 performs the braking operation as shown in FIGS. The relative movement speed in the radial direction of 2 may be accidentally accelerated although it should be attenuated originally, and the time until the tracking servo is turned on increases.

  Such erroneous detection of the moving direction due to the increase in eccentric acceleration, and hence inhibition of the pull-in to stable and high-speed tracking servo control occurs in the configuration described in Patent Document 1 and the like.

  Therefore, the frequency measurement circuit 46 is when the frequency of the tracking error signal is smaller than (or below) the reference frequency (the maximum frequency of the tracking error signal corresponding to the eccentric acceleration that can accurately output the moving direction detection signal). Only when the movement direction detection signal is accurate, the brake control circuit 45 is caused to perform the brake operation as shown in FIGS. As a result, even when the eccentric acceleration increases, it is possible to pull in the stable tracking control.

<< Second Embodiment >>
Next, a second embodiment of the objective lens movement direction detection device and the tracking control device having the objective lens movement direction detection device according to the present invention will be described with reference to the drawings. The optical disc apparatus in the second embodiment is different from the optical disc apparatus 1 in the first embodiment only in that an RF processing circuit 57 is provided instead of the RF processing circuit 7 in FIG. Are the same and will not be described.

  FIG. 6 is a block diagram showing detailed configurations of the RF processing circuit 57, the signal processing circuit 9, and the digital servo processing circuit 10. The same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

  Hereinafter, differences between the RF processing circuit 57 and the RF processing circuit 7 will be described. The RF signal generated by the RF amplifier 21 is sent to the subsequent RF signal processing unit. Similar to the AGC 22 in FIG. 2, the AGC 53 controls the gain of the RF amplifier 21 so that the amplitude of the RF signal output from the RF amplifier 21 is constant. In this case, the AGC 53 corresponds to a voltage for controlling the gain. An AGC control voltage is supplied to the amplitude amplifier circuit 51. Since information such as music is not recorded when the light beam spot is in the unrecorded area, this AGC control voltage is the maximum value that the AGC control voltage can take, and when it is in the recording area, it is smaller than the maximum value.

  The amplitude amplification circuit 51 amplifies the amplitude of the input AGC control voltage to the same amplitude as the wobble detection signal output from the amplitude detection circuit 33, and uses the amplified signal as an AGC signal for the two inputs of the switch circuit 41. Give to one end. That is, an AGC signal is given to the switch circuit 41 instead of the RF detection signal in FIG.

  The recording presence / absence detection circuit 52 receives the AGC control voltage, determines the recording or non-recording state of the optical disc 2 similarly to the recording presence / absence detection circuit 24, and outputs a recording presence / absence signal as the control voltage of the switch circuit 41. Specifically, when the AGC control voltage is the maximum value that the AGC control voltage can take, it is determined that the area is an unrecorded area, and a “no recording signal” is output, and the AGC control voltage is equal to the AGC control voltage. If it is smaller than the maximum value that can be taken, it is determined that the area is a recording area, and a “recorded signal” is output.

  Here, the AGC signal has the same period and the same phase as the RF detection signal in FIG. 3, and the AGC signal and the tracking error signal have a phase difference of 90 degrees in the radial direction of the optical disc 2. That is, it can be considered that the RF detection signal and the AGC signal in FIG. 3 are the same in generating the movement direction detection signal. Therefore, the movement direction detection signal when the recording presence / absence detection circuit 24 outputs a “recording presence signal” as the recording presence / absence signal is the same as that in FIG. 3, and the movement direction can be detected appropriately.

  In recent years, as the information recorded on optical discs has increased in density, the amplitude difference between the peaks and troughs of the RF detection signal waveform has decreased due to the narrower track pitch of lands and grooves and the groove depth conditions. In some cases, the S / N (Signal / Noise) ratio decreases, and the peaks and valleys of the RF detection signal are erroneously detected. This is because when the track pitch is narrower than the spot diameter of the light beam spot from the optical pickup 3, the amplitude of the RF detection signal is reduced (the information recording area is black and the unrecorded area is white). In this case, when the track pitch is narrowed, the RF signal is mixed with black and white and becomes gray, and the signal quality of the RF detection signal is deteriorated).

  Of course, if the positions of the peaks and valleys of the RF detection signal are erroneously detected, the moving direction cannot be detected accurately. Therefore, if the AGC signal is used instead of the RF detection signal in the recording area, the movement direction can be detected more accurately. This is because the AGC control voltage changes according to the amplitude of the RF signal, and if an AGC signal obtained by amplifying the AGC signal is used, the detection sensitivity in the moving direction is improved as compared with the case where the RF detection signal is used.

<< Other, deformation, etc. >>
In the above-described embodiments, DVD-R, DVD-RW / DVD + RW, and DVD-RAM are given as examples of the optical disk 2, but other optical disks include CD-R (Compact Disk Recordable) and CD-RW (Compact Disk). It may be an optical disk such as ReWritable) or BD (Blu-ray Disc), or may be a magneto-optical disk such as MD (Mini Disk) or MO (Magneto Optical disk). The optical disk apparatus may be an optical disk apparatus that performs reproduction / recording on each of the above-described CD-R, MD, etc. in addition to the optical disk apparatus 1.

  As a recording method of the optical disc, there is a recording method using a phase change characteristic, that is, a method using a characteristic that a multi-element material reversibly changes between crystalline and amorphous. In this phase change disk, recording is performed by irradiating a laser beam with a pulse to rapidly heat the recording film to a melting point or higher and then rapidly cooling it to make the recording film amorphous. This is performed by heating the crystallization temperature to a temperature equal to or higher than the melting point and then gradually cooling to return the amorphous portion to a crystalline state. Reproduction is performed by detecting the amount of reflected light by utilizing the fact that the reflectance differs between crystalline (high reflectance) and amorphous (low reflectance).

  In the case of a magneto-optical disk, recording is performed as follows. The recording film that has been uniformly magnetized in advance is irradiated with a laser beam to raise the temperature of the recording film locally to near the Curie temperature. Then, since the holding force of the recording film is reduced, a desired magnetic field (recording magnetic field) is applied from the outside to magnetize the recording film in the magnetic field direction. Erasing is performed by continuously irradiating a laser beam with a magnetic field corresponding to erasing, unlike a recording magnetic field. Reproduction is performed by utilizing the Kerr effect in which the polarization plane of the reflected light is slightly rotated according to the direction of magnetization.

  According to the objective lens moving direction detection device of the present invention, the moving direction of the objective lens can be accurately detected even for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded state and a recorded state are mixed. can do. By using this detection result, it is possible to achieve stabilization and speeding-up of tracking control after seek.

  Further, according to the tracking control device of the present invention, the moving direction of the objective lens is accurately detected even for an unrecorded optical disc in which no information is recorded or an optical disc in which an unrecorded status and a recorded status are mixed. In addition, stabilization and speeding-up of tracking control after seek can be realized.

1 is a schematic block diagram of an optical disc apparatus according to a first embodiment of the present invention. FIG. 2 is a detailed block diagram of an RF processing circuit, a signal processing circuit, and a digital servo processing circuit in FIG. 1. FIG. 3 is a diagram showing signal voltage waveforms when the recording presence / absence detection circuit in FIG. 2 outputs a recording presence signal. It is a figure which shows each signal voltage waveform in case the recording presence / absence detection circuit in FIG. 2 is outputting the recording non-signal. It is a figure which shows the voltage waveform of each signal of FIG. 2 when eccentric acceleration fluctuates. It is a detailed block diagram of the RF processing circuit, signal processing circuit, and digital servo processing circuit which concern on 2nd Embodiment of this invention. It is a figure for demonstrating the conventional tracking control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 2 Optical disk 3 Optical pick-up 4 Tracking actuator 5 Focus actuator 6 Thread motor 7 RF processing circuit 9 Signal processing circuit 10 Digital servo processing circuit 11 PWM signal generation circuit 12 PDM signal generation circuit 13 PWM driver 14 Motor driver 15 Spindle motor 16 System controller 17 Objective lens 21 RF amplifier 22, 53 AGC
23 RF detection BPF
24, 52 Recording presence / absence detection circuit 25, 33 Amplitude detection circuit 29 Matrix amplifier 30 Focus error signal generation circuit 31 Wobble signal generation circuit 32 Wobble detection BPF
34 tracking error signal generation circuit 35, 42 binarization circuit 41 switch circuit 43 D flip-flop 44 phase compensation circuit 45 brake control circuit 46 frequency measurement circuit 51 amplitude amplification circuit

Claims (4)

A track for recording information is formed having lands and grooves formed concentrically or spirally, and light emitted from a light source is coupled onto a disk-shaped recording medium in which wobbles are formed on the side walls of the track. In the objective lens moving direction detection device for detecting the moving direction in the radial direction of the disc-shaped recording medium, the objective lens for imaging and collecting the reflected light from the disc-shaped recording medium,
RF signal generating means for generating an RF signal obtained by reproducing the information recorded on the track;
Wobble signal generating means for generating a wobble signal corresponding to the wobble;
Tracking error signal generating means for generating a tracking error signal used for tracking control for causing the objective lens to follow the track;
Whether the area on the disc-shaped recording medium on which the emitted light is imaged is a recording area in which information is recorded or an unrecorded area in which information is not recorded in the RF signal. A recording presence / absence detecting means for detecting based on
When the detection result of the recording presence / absence detection means is a recording area, the moving direction is detected based on the RF signal and the tracking error signal, and when the detection result is an unrecorded area, the wobble signal and the tracking are detected. An objective lens moving direction detecting device, wherein the moving direction is detected based on an error signal. Search means for performing tracking control after seek control for moving the objective lens to a predetermined track,
The recording presence / absence detecting means, when the search means is operating, the area on the disc-shaped recording medium on which the emitted light is imaged is a recording area where information is recorded, or The objective lens moving direction detection device detects the moving direction of the objective lens when the search means is operating. The objective lens moving direction detection device according to claim 1, wherein: A track for recording information is formed having lands and grooves formed concentrically or spirally, and light emitted from a light source is coupled onto a disk-shaped recording medium in which wobbles are formed on the side walls of the track. In the objective lens moving direction detection device for detecting the moving direction in the radial direction of the disc-shaped recording medium, the objective lens for imaging and collecting the reflected light from the disc-shaped recording medium,
RF signal generation means for generating the RF signal, having an automatic gain control circuit that outputs a control voltage so that the amplitude of the RF signal reproduced from the information recorded on the track is constant;
Wobble signal generating means for generating a wobble signal corresponding to the wobble;
Tracking error signal generating means for generating a tracking error signal used for tracking control for causing the objective lens to follow the track;
Whether the area on the disc-shaped recording medium on which the emitted light is imaged is a recording area where information is recorded or an unrecorded area where information is not recorded is set as the control voltage. A recording presence / absence detecting means for detecting based on
When the detection result of the recording presence / absence detection means is a recording area, the moving direction is detected based on the control voltage and the tracking error signal, and when the detection result is an unrecorded area, the wobble signal and the tracking are detected. An objective lens moving direction detecting device, wherein the moving direction is detected based on an error signal. The objective lens moving direction detection device according to any one of claims 1 to 3,
Frequency measuring means for measuring the frequency of the tracking error signal;
Brake processing means for applying a brake on the movement of the objective lens in the radial direction of the disc-shaped recording medium based on the movement direction detected by the objective lens movement direction detection device when the frequency is smaller than a predetermined frequency; A tracking control device comprising:

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