JP2008269662A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical disk device having high accuracy and performing tracking pull-in stably and speedily only with software. <P>SOLUTION: The optical disk device is provided with a pickup 105 which reads information of an optical disk 101, coils 108 and 109 used for tracking/focus control of the pickup, a spindle motor 102 which rotates the optical disk, an analog signal processing circuit 114 which detects a lens error signal from an output signal from the pickup, and a microcomputer 113 which, on the basis of an FG signal corresponding to a disk rotation phase outputted from the spindle motor and a lens error signal of each disk rotation phase, detects and stores the maximum or minimum value of lens displacement of the pickup and starts tracking from the position of the disk rotation phase where the value of the lens error signal is maximized or minimized as a tracking start position when starting tracking. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus for recording or reproducing information on an optical disc.

  A high-speed and stable seek operation is required for an optical disc apparatus. The seek operation includes a long jump in which tracking is removed and a thread is moved at high speed, and a short jump in which speed control is performed while counting a zero cross of a tracking error by a track jump from a tracking state (for example, Patent Document 1 below) reference).

Usually, the address is read in the tracking state and the number of jump tracks is calculated. Next, when the number of tracks is large, the sled is moved at high speed in the tracking OFF state, and the sled is stopped before the target track. Next, the address is read as tracking ON, a short jump is performed, and the target track is reached. Of course, even when the normal tracking OFF state is turned ON, it is required to realize a high-speed and stable operation.
JP 2004-171610 A

  The conventional device counts the zero cross of the tracking error and detects the eccentricity, but this method is a count value in the FG section, and the point at which the eccentricity becomes maximum can be shifted due to the phase relationship with the FG. There is a large error. Further, assuming that the eccentricity is large, a dedicated high-speed counter circuit is necessary, and there is a problem that it cannot be handled only by software.

  The present invention has been made in view of the above-described points, and measures the eccentricity of the optical disk itself based on detection of the maximum or minimum value of the lens displacement of the pickup, which is highly accurate and does not require a dedicated high-speed counter circuit. An object of the present invention is to obtain an optical disc apparatus that can be handled only by software and can perform tracking pull-in stably and in a short time.

  As means for achieving the above object, a pickup for writing information to or reading information from an optical disk, pickup driving / adjusting means for performing tracking control and focus control of the pickup, and rotating the optical disk And a disk rotation means for outputting an FG signal corresponding to the disk rotation phase of the optical disk, a lens error detection means for detecting a lens error signal corresponding to a displacement of an objective lens constituting the pickup, the FG signal, Based on the lens error signal from the lens error detection means for each disk rotation phase, the maximum or minimum value of the lens displacement of the objective lens is detected and stored, and stored when the tracking control is started. Disk rotation position at which the maximum or minimum value is reached The position as a tracking start position is obtained by a control means for starting the tracking.

  According to the present invention, since the maximum value of the eccentricity itself is measured based on the detection of the maximum or minimum value of the lens displacement of the pickup, the accuracy is high, a dedicated high-speed counter circuit is unnecessary, and it can be handled only by software. Tracking pull-in can be performed stably and in a short time.

The optical disk apparatus of the present invention will be described below.
<Embodiment 1>
FIG. 1 is a block diagram showing the configuration of the optical disk apparatus according to Embodiment 1 of the present invention. In FIG. 1, an optical disk 101 is held in a detachable state on a flange 104 fixed to a shaft 103 of a spindle motor 102 that rotates the optical disk. The rotation speed of the spindle motor 102 is controlled so that a predetermined linear velocity is obtained at the spot position of the light beam. Further, the FG signal having a frequency proportional to the disk rotation phase output from the spindle motor 102 is used for detecting a speed signal in the rotation control by the microcomputer 113 as the control means. Further, the FG signal is frequency-divided by the frequency dividing circuit 116 to obtain one reference rotation phase signal REFP per rotation. When the microcomputer 113 counts the FG signal using the REFP signal as a reset signal, a disk rotation phase signal (data) is obtained.

  The pickup 105 includes a laser diode 106, a light receiving unit 107 including a plurality of photodiodes, a half mirror, an objective lens, and a magnet (not shown), and a movable unit that can be displaced in the tracking direction and the focus control direction. It comprises a tracking coil 108 and a focus coil 109 for control.

  Further, the entire pickup 105 is configured to be movable in the radial direction of the disk 101. This is realized by the microcomputer 113 controlling the thread motor 110 attached to the lead screw 111 screwed with the female screw portion attached to the pickup 105 via the drive circuit 112.

  The laser light emitted from the laser diode 106 is irradiated onto the disk 101 via the objective lens, and is modulated and reflected by the recording signal and the guide groove. This light is incident on the light receiving unit 107 through a half mirror. The beam is composed of three beams by an optical system such as a diffraction grating (not shown in detail). The analog signal processing circuit 114 detects and outputs the tracking error signal TE, the focus error signal FE, and the lens error signal LE from the signal photoelectrically converted by the pickup 105. Further, these output signals are converted from analog to digital by the AD converters 118 to 120 and input to the microcomputer 113.

  FIG. 2 is a detailed explanatory diagram of the light receiving unit 107 and the analog processing circuit 114 in FIG. Here, A, B, C, D, E, F, G, and H are the outputs of one 4-division photodiode and two 2-division photodiodes constituting the light receiving unit 107, and the analog processing circuit 114 is The tracking error signal TE, the focus error signal FE, and the lens error signal LE can be obtained by performing the following analog calculation by a known method.

FE = (A + C)-(B + D)
TE = ((A + D) − (B + C)) + ((E−F) + (G−H))
LE = ((A + D)-(B + C))-((E-F) + (GH))

  An output proportional to the amount of movement of the lens in the tracking direction can be obtained from the lens error signal LE. In the midpoint servo, this lens error signal is used as a servo error signal, and an error signal is obtained using LE at the lens center position as a target value, and this is feedback controlled. Thereby, even when the sled is moved, the lens is positioned at the center position without vibrating.

  In FIG. 1, the tracking error signal TE is converted from analog to digital by an AD converter 118 and taken into the microcomputer 113. Similarly, the focus error signal FE is converted from analog to digital by the AD converter 119 and taken into the microcomputer 113. The lens error signal LE is taken into the microcomputer 113 via the AD converter 120.

  The microcomputer 113 is connected to a ROM, and stores programs and fixed data. A RAM is also connected to store variable values and the like. Further, a flash ROM for storing initial setting values and the like is connected.

  Further, the DA converter 121 is connected to the microcomputer 113, outputs data obtained by calculating the tracking control drive signal, and drives the tracking control coil 108 via the drive circuit 123 with this value. Similarly, a DA converter 122 is connected to the microcomputer 113, outputs data obtained by calculating a focus control drive signal, and drives the tracking control coil 109 via the drive circuit 124 with this value.

  Further, an inner peripheral switch 117 is attached to the fixed portion, and when the movable portion reaches the innermost peripheral position due to the movement of the sled, the switch is turned on, and this is read and detected by the microcomputer 113.

  FIG. 3 is an explanatory diagram of the long jump operation in the seek operation in the first embodiment shown in FIG. First, in a normal tracking state (TRON: the tracking actuator is controlled based on the TE signal by the tracking servo to keep the on-track state), the microcomputer 113 reads the address from the disk 101 by the pickup 105, and then the target When the distance to the track at the address is calculated, and the distance to the track at the target address is greater than a predetermined value, the thread motor 110 is controlled to control a known long jump (the tracking servo is turned off and the tracking actuator is controlled). Track jump the light beam spot). In the long jump, the midpoint servo is used and the thread motor 110 is rotated by the number of steps obtained by calculation, and the pickup 105 is moved immediately before the target track at high speed. Then, after waiting for a rotation phase that facilitates tracking pull-in based on the FG signal from the spindle motor 102, the tracking is turned on, the address is read from the disk 101 again by the pickup 105, the remaining number of tracks is calculated, and the spindle motor 102 is Control to start a known short jump.

  When a disk with large eccentricity is used, a problem occurs at this time, that is, when tracking is turned on.

  FIG. 4 shows a track locus in the eccentric disk. The solid line is the locus when there is no eccentricity (actually it is a spiral but is shown closed). The radial line corresponds to the FG number indicating the rotational phase, and in the first embodiment, it has a structure of 16 divisions per round (16 pulses). A dotted line is a track locus at the time of an eccentric disk.

  FIG. 5 shows a lens error signal LE that is the amount of displacement in the tracking direction of the lens during following by the tracking servo. The higher level is on the outer peripheral side, and the lower level is on the inner peripheral side. In this figure, the displacement corresponds to the FG number in FIG. 4, P5 is displaced to the outermost periphery, and P13 is displaced to the innermost periphery. Thus, the lens error signal LE indicates the displacement of the lens itself, and the microcomputer 113 can know the position of the lens by AD-converting this signal by the AD converter 120. Further, the points on the innermost circumference and outermost circumference are inflection points of the trajectory, the track straddling is minimized, and the tracking becomes the most easily drawn point.

  FIG. 6 shows a tracking error signal TE when the eccentricity is small, a tracking error zero cross signal TES, and a lens error signal LE when the track follow is performed in a state corresponding to the rotation phase. Since the frequency of the tracking error signal TE is low, it is easy to pull in. FIG. 7 shows a slightly large eccentricity, and FIG. 8 shows a state where the eccentricity is further large. It can be seen that the position where the lens error signal LE is maximized / minimized decreases the frequency of the tracking error signal TE and is easy to pull in. However, as the eccentricity increases, the retractable time becomes shorter.

  FIG. 9 and FIG. 10 are flowcharts showing the contents of a program at the time of tracking pull-in control by the microcomputer 113 as control means and detection of the maximum or minimum value of lens displacement. First, referring to FIG. 10, which is a flowchart of a program for detecting the FG number that maximizes the lens error signal LE and the FG number that minimizes the lens error signal LE, the microcomputer 113 detects the maximum or minimum value of the lens displacement. Explain the contents.

  In step S1001, tracking is turned ON. Since the measurement is performed once, there is no problem even if the pull-in at this time takes time. In step S1002, the maximum value LEMAX and the minimum value LEMIN of the lens error signal LE are initialized. Here, the AD conversion value is 8-bit data. Therefore, LEMIN = 0xFF. In step S1003, an FG number is read based on an FG signal having a frequency proportional to the rotational speed output from the spindle motor 102. In step S1004, it is checked whether the measurement for one rotation is completed based on the reference rotation phase signal REFP from the frequency dividing circuit 116. When the FG number goes around once, the process is over.

  If the measurement for one rotation is not completed, step S1005 is performed. Here, the lens error signal LE is taken in after AD conversion. In step S1006, the measured value LE of the lens error signal LE is compared with the maximum value LEMAX thus far. If LE is greater than LEMAX, LEMAX is replaced with LE in step S1007, and the count value FGCNT of the FG number at that time is set to LEMAXFG in step S1008. In step S1009, the measured value LE of the lens error signal LE is compared with the previous minimum value LEMIN. If LE is smaller than LEMIN, LEMIN is replaced with LE in step S1010, and the count value FGCNT of the FG number at that time is set to LEMINFG in step S1011. Thereby, it is possible to know the FG number when LE is maximized and minimized.

  In the first embodiment, since the value of the lens error signal LE is captured over the entire circumference of one rotation of the disk, the maximum value and the minimum value can be detected without omission. The position is always in the FG number range at that time. However, in the conventional method, the number of tracking error zero-cross signals TES within the FG number range becomes a problem, and the maximum value and the minimum value do not always fall within that range.

  Next, referring to FIG. 9, which is a flowchart of a tracking pull-in control program executed by the microcomputer 113, the control contents when pulling in with tracking turned ON will be described. Since the FG number to be drawn in is already known, it is sufficient to wait until the position is reached. In step S901, the FG number is read based on the FG signal output from the spindle motor 102. In step S902, it is checked whether the count value FGCNT of the FG number is equal to LEMAXFG. If they are equal, the process proceeds to step S904, where tracking is turned ON. In step S903, it is checked whether the count value FGCNT of the FG number is equal to LEMINFG. If they are equal, the process proceeds to step S904, where tracking is turned ON. Otherwise, the process proceeds to step S901. These processes do not require interrupt processing and do not require special hardware.

  In the first embodiment, as described above, both the maximum value and the minimum value of the lens error signal LE are measured. If one of them is measured and the FG number is specified, the 180 ° phase is measured. The shifted position may be the other pullable phase. This is possible because much of the eccentricity is sinusoidal.

  Further, since the pulling may be more stable when tracking is turned on immediately before the FG number position where the detected eccentricity is maximum, the FG number immediately before the measurement position may be set as the ON timing. Further, after obtaining the immediately preceding FG number, a slight time may be measured by a soft timer and turned on after the lapse.

  Further, in the first embodiment, the case where the tracking is turned on after the mid-point servo has been described. However, the present embodiment is applicable to the case where the tracking is turned on from the normal track OFF state, and is highly effective.

<Embodiment 2>
FIG. 11 is a block diagram showing the configuration of Embodiment 2 of the optical disc apparatus according to the present invention. In the second embodiment shown in FIG. 11, the same parts as those of the first embodiment shown in FIG. In the second embodiment shown in FIG. 11, in contrast to the configuration of the first embodiment shown in FIG. 1, a reflection plate is attached to the movable portion of the pickup 105, and a light reflection sensor 125 as a lens position detection means is further provided in the fixed portion. It is attached.

  Here, when the objective lens of the pickup 105 is in the proper position, the signal obtained from the light reflection sensor 125 is adjusted to the reference level, and when the objective lens is deviated from the proper position, the signal obtained from the light reflection sensor 125 is obtained. The signal is changed to a level proportional to the amount of deviation of the objective lens with the reference level as the center. The lens error signal LE is directly detected by the light reflection sensor 125 and output to the AD converter 120 for AD conversion. Analog-digital conversion can be performed by the device 120 and input to the microcomputer 113.

  That is, in the first embodiment, the analog processing circuit 114 performs an analog operation based on the outputs of one quadrant photodiode and two two-division photodiodes that constitute the light receiving unit 107 of the pickup 105, and the lens error signal LE. However, in the second embodiment, the lens error signal LE can be directly detected by the light reflection sensor 125 as the lens position detection means, and the light reflection sensor 125 can be the lens error detection means.

  Other configurations and operations of the second embodiment are the same as those of the first embodiment, and similar effects can be obtained.

  The present invention can be applied to various optical disc recording / reproducing apparatuses such as a DVD player / recorder and a BD player / recorder.

1 is a block diagram showing a configuration of a first embodiment of an optical disc device according to the present invention. FIG. 2 is a detailed explanatory diagram of a light receiving unit 107 and an analog processing circuit 114 in FIG. 1. It is explanatory drawing of the operation | movement of the long jump in the seek operation | movement in embodiment of FIG. It is explanatory drawing which shows the track locus in the eccentric disk for demonstrating operation | movement of embodiment of FIG. It is explanatory drawing which shows the lens error signal LE used as the displacement amount to the tracking direction of the lens at the time of following by the tracking servo for demonstrating operation | movement of embodiment of FIG. The tracking error signal TE when there is little eccentricity for explaining the operation of the embodiment of FIG. 1, the zero-cross signal TES of tracking error, and the lens error signal LE when following the track in a state corresponding to the rotational phase. FIG. It is a wave form diagram in case eccentricity is a little larger than FIG. 6 for demonstrating operation | movement of embodiment of FIG. It is a wave form diagram in case eccentricity is still larger than FIG. 7 for demonstrating the operation | movement of embodiment of FIG. It is a flowchart which shows the content of the program at the time of the tracking pull-in control by the microcomputer 113 as a control means in FIG. It is a flowchart at the time of the detection of the maximum value or the minimum value of the lens displacement by the microcomputer 113 as the control means in FIG. It is a block diagram which shows the structure of Embodiment 2 of the optical disk apparatus based on this invention.

Explanation of symbols

101 optical disk 102 spindle motor (disk rotating means)
105 Pickup 108, 109 Coil (Pickup drive / adjustment means)
110 Thread motor 113 Microcomputer (control means)
114 Analog signal processing circuit (lens error detection means)
125 Light reflection sensor (Lens error detection means)

Claims (4)

A pickup for writing information to or reading information from an optical disc;
Pickup drive / adjustment means for performing tracking control and focus control of the pickup;
A disk rotating means for rotating the optical disk and outputting an FG signal corresponding to a disk rotation phase of the optical disk;
Lens error detection means for detecting a lens error signal in accordance with the displacement of the objective lens constituting the pickup;
The maximum or minimum value of the lens displacement of the objective lens is detected and stored based on the FG signal and the lens error signal for each disk rotation phase, and the stored maximum value when the tracking control is started. Or a control means for starting tracking with the position of the disk rotation phase that is the minimum value as the tracking start position,
Optical disk device provided. Further comprising a sled motor for moving the pickup;
The control means performs mid-point servo control based on the lens error signal during a long jump by the thread motor control, and then the disk rotation phase at which the value of the lens error signal becomes the maximum value or the minimum value. 2. The optical disc apparatus according to claim 1, wherein tracking is started with the position as a tracking start position.   3. The tracking start position according to claim 1, wherein the control unit sets a position where a 180 ° phase shift of the disk rotation phase at which the value of the lens error signal becomes the maximum value or the minimum value as a tracking start position. Optical disk device.   4. The control unit according to claim 1, wherein the control unit sets a predetermined time before the disk rotation phase at which the value of the lens error signal becomes the maximum value or the minimum value as a tracking start position. 5. Optical disk device.

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