JP2006228363A - Optical disk recording and reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk recording and reproducing apparatus where amplitude fluctuation of a tracking error signal due to eccentricity caused by a DPP tracking system is corrected by a simple method without requiring a memory cost. <P>SOLUTION: The apparatus comprises an optical pickup position detection part 9 for detecting an optical spot position, an FG pulse generation part 3, a rotation angle position detection part 4 of an optical disk, rotation speed detection part 14 of the optical disk, a track error signal period detection part 15 for detecting the period of the track error signal generated when an optical spot transverses a plurality of tracks when the optical spot is fixed to a prescribed position, and a minimum periodic angle position detection part 15 for obtaining a rotation angle position where the period of the track error signal is minimum. The eccentricity of the optical disk is calculated from the minimum period of the track error signal and the rotation speed of the optical disk, and the amplitude fluctuation of the tracking error signal at the optical spot position is corrected based on the eccentricity and the rotation angle position where the period becomes minimum. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an optical disc recording / reproducing apparatus using an optical disc such as a CD, a DVD, or a BD (Blue-ray Disc), and in particular, the amplitude of a track error signal when the track of the optical disc is eccentric with respect to the rotation center of the optical disc. It is also about correction.

Due to the accuracy of the center hole of the optical disk and the mounting error when the optical disk is fixed to the spindle motor, the center of the track of the optical disk and the rotation axis of the spindle motor do not always match. Rotate.
As a tracking control method for an optical disc apparatus, a three-beam differential push-pull (DPP) method is often used. The track error (TE) signal at this time is constituted by the difference between the main beam output and the sum of the two sub beam outputs. Here, if the optical disc is decentered, the tracking position of each sub beam is shifted, so that the sub beam output sum changes and the amplitude of the track error signal changes. That is, in the DPP tracking method, if there is an eccentricity, the track error signal amplitude also changes as the optical disk rotates. (For example, refer to Patent Document 1, page 2-4, FIG. 8-17.)

If the amplitude variation of the track error signal due to such eccentricity is large, the track servo is affected by the amplitude variation, and a constant loop gain cannot be obtained. A track error signal may be input to a hysteresis comparator and used as various control signals. However, if there is a decrease in amplitude, the threshold value of the comparator may not be reached, and the signal may be lost.
Recently, as the capacity of optical discs has increased, the track pitch has become increasingly narrower. For example, a CD-ROM has a track pitch Pt = 1.6 μm, a DVD-ROM has a track pitch Pt = 0.74 μm, and a BD has a track pitch Pt = 0.32 μm. For this reason, the fluctuation of the amplitude of the track error signal due to the eccentricity of the optical disk has become a problem that cannot be ignored.

Therefore, a method for canceling the amplitude fluctuation of the track error signal due to the eccentricity of the optical disk has been proposed (for example, see Patent Document 1).
An example of a conventional track error amplitude correction apparatus will be described with reference to FIG.
An optical disc apparatus provided with a track error amplitude correction device includes an optical disc 1, a spindle motor 2, an FG pulse generator 3, a rotation angle detector 4, an optical pickup 5, an actuator 6, an optical pickup moving means 7, and an optical pickup position detector 9. , A TE signal generation unit 10, a variable gain amplifier 11, an ACT driver 12, a TE signal amplitude measurement unit 20, a correction gain storage / setting unit 21, and a CPU (not shown) for controlling them.
The optical pickup 5 emits a laser beam composed of a main beam and two sub beams to the optical disc 1 and detects the reflected light using a split sensor. The TE signal generator 10 generates a DPP track error signal from a plurality of detection signals obtained by the optical pickup.
The rotation angle detection unit 4 detects and outputs the rotation angle position θ of the spindle motor 2 based on the FG pulse generated by the FG (Frequency Generator) pulse generation unit 3.
The optical pickup position detector 9 detects a radial position r from the rotation center of the optical pickup. When the optical disk is mounted on the spindle motor, the polar coordinates (r, θ) of the light spot position with respect to the optical disk can be detected by the rotation angle detection unit and the optical pickup position detection unit.
When the motor is rotated and the focus servo is applied without applying the tracking servo and the focus servo is applied, the track of the optical disk crosses under the light spot due to the eccentricity, and a sinusoidal track error signal is periodically output. . The TE signal amplitude measuring unit 20 measures the track error signal amplitude according to the measured rotation angle position θ on the disk and the radius position r, and stores the track error signal amplitude together with the rotation angle position θ and the radius position r. To do.
At the time of recording / reproducing, the gain of the variable gain amplifier 11 is adjusted based on the stored track error signal amplitude so as to suppress the amplitude fluctuation at each rotation angle position θ and radial position r of the disk. Get a track error signal without. Then, based on the amplitude correction TE signal in which the amplitude variation is corrected, the actuator 6 is driven by the ACT driver 12 for tracking.
JP-A-9-231594 (page 4-6, Fig. 1-3)

  However, in the conventional example, the amplitude of the track error signal must be measured for each rotation angle position θ and radius position r of the light spot on the optical disk, and the track error signal for each rotation angle position θ and radius position r. A memory for storing the amplitude of the signal is also required.

  Accordingly, the present invention has been made to solve the above-described problems. A track error caused by the eccentricity of an optical disk can be performed by a simple method without measuring the track error signal amplitude and without increasing the memory cost. An object of the present invention is to provide an optical disk track error amplitude correction apparatus that corrects fluctuations in signal amplitude, ensures a stable servo gain, and improves reliability as a control signal.

  The present invention relates to an optical pickup (optical pickup 5) having a plurality of divided light receiving regions for irradiating a rotating optical disc with laser light, detecting return light reflected by the optical disc and converting it into an electrical signal, A track error signal generation circuit (TE signal generation unit 10) that calculates an electrical signal to generate a track error signal, and a signal that performs track positioning of the optical disk irradiated with the laser beam based on the track error signal In an optical disk recording / reproducing apparatus having an output driver circuit (ACT driver 12), an optical pickup position detection unit (optical pickup position detection unit 9) that detects a light spot position from a rotation center on the disk to a light spot; Rotation to detect the reference position of the rotation angle of the spindle motor that rotates the optical disc Based on the pulse signal generated by the reference position detector, a pulse generation unit (FG pulse generation unit 3) that generates a multiplied pulse signal, and by counting the number of pulses from the reference position of the multiplied pulse signal A rotation angle detection unit (rotation angle detection unit 4) for detecting the rotation angle position of the optical disk, and a rotation speed detection unit (rotation speed detection) for detecting the rotation speed of the optical disk from the multiplied pulse signal based on a reference clock. 14) and a track error signal period for detecting a period of the track error signal at the rotation angle generated when the light spot crosses a plurality of tracks when the light spot is fixed at a predetermined position on the optical disc. A detection unit (TE signal cycle detection unit 15), and a minimum of cycles of the track error signal corresponding to the rotation angle; The rotation angle position in a predetermined period is detected by a minimum cycle angle position detection unit (TE signal cycle detection unit 15) that is obtained based on the number of pulses counted by the rotation angle detection unit, and the track error signal cycle detection unit. Further, an eccentricity calculation unit (eccentricity calculation / storage unit 16) that calculates an eccentricity amount of the optical disk based on the minimum period of the track error signal and the rotation speed of the optical disk detected by the rotation speed detection unit; Correction gain setting means for correcting the amplitude of the track error signal at the rotation angle position of the optical disk and the light spot position based on the eccentric amount of the optical disk and the rotation angle position of the optical disk at which the track error signal obtains the minimum cycle. There is provided an optical disk recording / reproducing apparatus comprising a correction gain calculation / setting unit 17).

  According to the present invention, an optical pickup position detection unit that detects a light spot position from the rotation center on the disk to a light spot, and a rotation angle reference position detection that detects a rotation angle reference position of a spindle motor that rotates the optical disk. A pulse generator for generating a multiplied pulse signal based on the pulse signal generated by the detector, and a rotation for detecting the rotation angle position of the optical disc by counting the number of pulses from the reference position of the multiplied pulse signal An angle detection unit; a rotation speed detection unit that detects a rotation speed of the optical disk from the multiplied pulse signal based on a reference clock; and the light spot when the light spot is fixed at a predetermined position on the optical disk. Detects the period of the track error signal at the rotation angle that occurs when the vehicle crosses multiple tracks A track error signal period detector that detects the rotation angle position in a minimum period among the periods of the track error signal corresponding to the rotation angle based on the number of pulses counted by the rotation angle detector. The amount of eccentricity of the optical disk based on the period angle position detector, the minimum period of the track error signal detected by the track error signal period detector and the rotational speed of the optical disk detected by the rotational speed detector Based on the amount of eccentricity of the optical disc, the amount of eccentricity of the optical disc, and the rotational angle position of the optical disc at which the track error signal obtains the minimum period, Since there is a correction gain setting means to correct the amplitude, do not measure the track error signal amplitude. , Track error of optical disc with stable servo gain and improved reliability as control signal by correcting fluctuation of track error signal amplitude due to eccentricity of optical disc by simple method, without memory cost An amplitude correction apparatus can be provided.

A track error amplitude correction apparatus for an optical disk recording / reproducing apparatus according to each embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a block diagram showing a track error amplitude correcting apparatus of an optical disk recording / reproducing apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the track error signal obtained from the eccentric optical disk and the FG number representing the rotational angle position of the motor in the track error amplitude correction apparatus of the present invention. FIG. 3 is an explanatory view of the eccentricity in the track error amplitude correction apparatus of the present invention. FIG. 3A shows the geometric relationship between the light spot position, the rotation center, and the track center, and FIG. A change in position of the observed light spot position with the rotation of the motor is shown, and (C) shows a track deviation of the sub beam resulting from a track angle deviation due to eccentricity. 4A and 4B are flowcharts of the track error amplitude correcting apparatus according to the present invention. FIG. 4A shows an eccentricity measuring operation, and FIG. 4B shows a track error amplitude correcting operation during recording and reproduction.
Example 1

  As shown in FIG. 1, the track error amplitude correction apparatus according to the present invention includes an optical disc 1, a spindle motor 2, an FG pulse generator 3, a rotation angle detector 4, an optical pickup 5, an actuator 6, an optical pickup moving means 7, an origin. Sensor 8, optical pickup position detection unit 9, TE signal generation unit 10, variable gain amplifier 11, ACT driver 12, reference clock generator 13, rotation speed detection unit 14, TE signal period detection unit 15, eccentricity calculation / storage unit 16 , A correction gain calculation / setting unit 17 and a CPU (not shown) for controlling them. The configuration of the present invention is the same as the configuration shown in FIG. 5 of the conventional example except for the correction gain setting unit indicated by the broken line frame.

The optical pickup 5 emits a laser beam composed of a main beam and two sub beams to the optical disc 1 and detects the reflected light using a split sensor. The TE signal generator 10 generates a DPP track error signal from a plurality of detection signals obtained by the optical pickup. The ACT driver 12 drives the actuator 6 for tracking based on the amplitude correction TE signal corrected by the variable gain amplifier 11 which can set the gain for each rotation angle position θ and radius position r of the optical disk. .

The optical pickup moving means 7 moves the optical pickup in the radial direction of the optical disk by a stepping motor and a lead screw.
The optical pickup position detection unit 9 detects the position of the optical pickup. The origin sensor 8 provided on the inner circumference side of the optical disk counts how many pulses the stepping motor has rotated from there, and the numerical value of the spindle motor is calculated from that value. The optical pickup position in the radial direction (r = Xp) with the rotation center position set to 0 is calculated and stored.

On the other hand, the FG pulse generation unit 3 detects the rotation phase of the spindle motor 2 that rotates the optical disk, detects the magnet at the reference position of the motor with a hall sensor, and generates an FG pulse signal obtained by dividing the rotation of the disk by Nn. Generate and output with reference position pulse.
The rotation angle detection unit 4 counts the FG pulse signal, adds an FG number N (N: 0 to Nn-1) with the reference position set to 0, and rotates the rotation angle position (θ = 2π / Nn * N) is detected and output.
When the optical disk is mounted on the spindle motor, the polar coordinates (r, θ) of the light spot position with respect to the optical disk can be detected by the rotation angle detection unit and the optical pickup position detection unit.
Next, a configuration related to a correction gain setting method which is a feature of the present invention will be described.

The rotation speed detection unit 14 detects the rotation speed of the motor from the FG pulse signal using a reference clock sufficiently higher than the frequency of the FG pulse generated by the reference clock generator 13. In this embodiment, the FG pulses corresponding to the half rotation of the disk are counted, and the time required for the half rotation of the disk (T = Tmot, the number of pulses) is stored.

When the fixed light spot crosses an eccentric disk track, a sinusoidal track error signal is periodically output. FIG. 2 is a diagram showing the relationship between the track error signal at this time and the FG number representing the rotational angle position of the motor, and the amplitude of the track error decreases every half of the disk. Further, as the amplitude decreases, the cycle of the track error signal becomes shorter, and the cycle becomes the shortest at the minimum amplitude portion.
The TE signal cycle detection unit 15 detects the time of one cycle of the sine wave-shaped track error signal, and counts and measures the number of pulses of the reference clock. In the present embodiment, the number of clocks of the shortest track error signal period (T = Tmin) that minimizes the number of the reference clocks is stored from among the plurality of track error signal periods obtained during the half circumference of the disk. At the same time, the FG number (N = Np) from which the smallest number is obtained in the half circumference of the disk is obtained from the FG counter 4 and stored.

The eccentricity calculation / storage unit 16 calculates the amount of eccentricity from the numerical values of Tmot and Tmin (the calculation formula will be described later), and stores the amount of eccentricity E.
The correction gain calculation / setting unit 17 corrects the amplitude drop due to the eccentricity of the track error signal from the eccentricity (E), the radial position (r) of the optical pickup, and the rotational angle position (θ) of the disk. A gain is obtained, a correction gain corresponding to the radial position (r) and the rotation angle position (θ) is set in the variable amplifier 11, and the amplitude of the track error signal is kept constant.
Next, the correction gain setting method of the present invention configured as described above will be specifically described with reference to FIG.

First, the variation in the track position due to the eccentricity E will be described. FIG. 3A shows the geometrical relationship between the light spot S, the rotation center O, and the track center R when the optical disk is mounted with a deviation E from the rotation center in the upper part of the drawing. r is the distance from the rotation center to the light spot S, r0 is the distance from the track center to the light spot S, and θ is the motor rotation angle position.
Here, if the cosine theorem is applied to ΔROS and E << r, then r = r0 + E * sin (θ) where θ = 2π (N−Np) / Nn
It becomes. That is, as shown in FIG. 3B, the distance from the center of rotation to the track changes in a sine wave shape with the amount of eccentricity E as an amplitude.

Next, a method for calculating the eccentricity E by measuring the shortest track error signal period Tmin and the half rotation period Tmot of the motor will be described.
The maximum speed at which the light spot moves on the disc in the track width direction is
Vmax = Pt / Tmin
It becomes. Here, Pt represents the track pitch.
On the other hand, assuming the eccentricity E, the track position moving speed V with respect to the fixed light spot is
V = dr / dt = E * π / Tmot * cos (ωt)
It becomes. However, the rotational angular velocity of the disk is ω = π / Tmot.
Therefore, if the two maximum speeds are equal, the eccentricity E can be calculated by the following equation.
E = Tmot / Tmin * Pt / π Pt: Track pitch

With reference to FIG. 3C, the track deviation of the sub beam due to the eccentricity will be described.
Since the optical sensor system using the main beam and the two sub beams is correctly set with respect to the center of rotation, if there is a track angle deviation δ (∠RSO in FIG. 3A) due to eccentricity, a broken line in FIG. As shown, the two sub beams cause a track shift in the opposite directions with the main beam as the center. In general, since the angle between the axis connecting the sub-beams and the track longitudinal direction is very small, if L = (distance between sub-beams) / 2, this amount of deviation can be approximated by L * δ. ■ Φ is
■ Φ = 2π / Pt * L / r0 * E * cos (θ) L = (distance between sub-beams) / 2
It becomes.

Next, when there is this phase shift ΔΦ, the track error signal output TE of the DPP method is
TE = 1/4 * sin (Φ + ■ Φ) + 1/4 * sin (Φ− ■ Φ) + 1/2 * sin (
Φ)
= 1/2 * (1 + cos (■ Φ)) * sin (Φ)
It becomes. However, (PHI) shows a tracking phase.
Here, assuming that Φ is very small,
TE amplitude coefficient = 1/2 * (1 + cos (■ Φ))
≈ 1-1 / 8 * (2π / Pt * L / r0 * E) ^ 2 * cos (2θ)
= 1−A * (1 / Xp) ^ 2 * cos (2θ)
It becomes. However, A = 1/8 * (2π / Pt * L * E) ^ 2.
That is, the phase shift-voltage TE conversion curve, which should be sin (Φ), is modulated by the TE amplitude coefficient. For this reason, the TE output is subjected to a sinusoidal modulation once in half rotation by cos (2θ) like the track error signal at the time of eccentricity measurement shown in FIG. 2, and the modulation amplitude is the square of the eccentricity E. And inversely proportional to the square of the radial position Xp.
However, the above assumption does not necessarily hold when the light spot position is the innermost circumference and the eccentricity E is large.

As described above, the correction gain for correcting the amplitude of the track error needs to be determined in consideration of the eccentric amount and the disk reading position.
Next, the operation of the present invention configured as described above will be described separately for eccentricity measurement and TE signal amplitude correction during recording and reproduction.

First, a method for measuring eccentricity will be described with reference to the flowchart of FIG.
The optical pickup is moved to the origin sensor installed on the inner periphery, and the radial position information is reset (step S1). Then, the optical pickup is moved near the center of the disk, the disk is rotated, and focus servo is applied (step S2). The number of reference clocks corresponding to a half rotation of the disk is measured and stored as the disk rotation speed (Tmot) (step S3).
Then, as the frequency of the track error signal, the number of reference clocks is measured within one cycle of the track error signal as shown in FIG. 2, and it is measured over a half of the disk (step S4). The minimum number (Tmin) and the FG number representing the rotation angle at which the minimum number is obtained are stored (Np) (step S5).
The amount of eccentricity (E) is obtained by the following equation and stored (step S6).
E = Tmot / Tmin × Pt / π where Pt: track pitch

Next, the amplitude correction method of the TE signal will be described with reference to the flowchart FIG.
The track servo is applied and the reproduction or recording operation is started (step S11).
As an initial setting, an FG number N representing the rotation angle position where the light spot on the disk at that moment is present is measured and stored (step S12).
An FG number N representing the light spot rotation angle position on the disk is acquired (step S13).
The measured N is compared with the stored N. If it is different, the process proceeds to the next step, and if it is the same, the operation is repeated to wait for the update (step S14).
The FG number N representing the new rotation angle position is stored (step S15).
The optical pickup position, that is, the light spot position Xp is acquired and stored (step S16).
As described above, parameters necessary for the calculation of amplitude correction are secured.
Here, the track error amplitude coefficient at the light spot position r = Xp, θ = 2π (N−Np) / Nn is obtained by the following equation (step S17).
TE amplitude coefficient = 1/2 * (1 + cos (■ Φ))
However, ■ Φ = 2π / Pt * L / r0 * E * cos (θ)
θ = 2π (N−Np) / Nn, r0≈r = Xp
Np, E, N, Xp: measured value, Pt, L, Nn: constant Next, from the track error amplitude coefficient obtained from the above equation, the position (Xp) of the optical pickup and the current FG number (N ) To obtain the track error correction gain and set the gain of the amplifier (step S18).
As a result, the amplitude fluctuation of the track error due to the eccentricity can be corrected regardless of the light spot reading position (radius position, rotation angle position).

As described above, according to the embodiment of the present invention, since there is the above-described configuration, the amplitude variation of the track error signal generated from the eccentric optical disc is corrected, the reading position in the radial direction of the disc, and the disc rotation angle. Regardless of the position, the amplitude of the track error signal can be made constant, and the problems caused by stabilization of the loop gain and reduction of the track error amplitude are eliminated.
In addition, since the amplitude correction amount is calculated from the measurement of the time interval using the FG pulse, the measurement of the rotation angle position and the pickup position, the amplitude fluctuation of the track error signal can be performed by a simple method without adding a new mechanism. Can be corrected. Furthermore, if only the amount of eccentricity and the reference rotation angle position are stored, the other parameters can be calculated directly using the measured values, so that the present invention can also be applied to a device having a small memory capacity.

In the embodiment, it has been described that the pickup position is measured Nn times per rotation. However, it is sufficient to measure the pickup position once at an appropriate number of rotations.
Further, although this method has been described with the DPP tracking method, the TE amplitude coefficient is set to cos (■ Φ).
As a result, it can be applied to the sub beam of the three beam method.

It is a block diagram which shows the track error amplitude correction apparatus of the optical disk recording / reproducing apparatus in embodiment of this invention. It is a graph which shows the relationship between the track error signal obtained from the eccentric optical disk in the track error amplitude correction apparatus of this invention, and FG number showing the rotation angle position of a motor. It is explanatory drawing of the eccentricity in the track error amplitude correction apparatus of this invention, (A) is explanatory drawing which shows the geometrical relationship with a light spot position, a rotation center, and a track center, (B) was seen on the track | truck. FIG. 4C is an explanatory diagram showing a change in position of the light spot position accompanying the motor rotation, and FIG. 4C is an explanatory diagram showing a sub-beam track shift caused by a track angle shift due to eccentricity. In the flowchart of the track error amplitude correcting apparatus of the present invention, (A) shows an eccentricity measuring operation, and (B) shows a track error amplitude correcting operation at the time of recording / reproducing. It is a block diagram which shows the track error amplitude correction apparatus of the optical disk recording / reproducing apparatus in a prior art example.

Explanation of symbols

1 optical disk, 2 spindle motor, 3 FG pulse generator, 4 rotation angle detector, 5 optical pickup, 6 actuator, 7 optical pickup moving means 7, 8 origin sensor, 9 optical pickup position detector, 10 TE signal generator, DESCRIPTION OF SYMBOLS 11 Variable gain amplifier, 12 ACT driver, 13 Reference clock generator, 14 Rotational speed detection part, 15 TE signal period detection part, 16 Eccentric calculation / storage part, 17 Correction gain calculation / setting part

Claims (1)

An optical pickup having a plurality of divided light receiving areas for irradiating a rotating optical disk with laser light, detecting return light reflected by the optical disk and converting it into an electric signal, and a track error signal by calculating the electric signal An optical disc recording / reproducing apparatus comprising: a track error signal generating circuit that generates a signal; and a driver circuit that outputs a signal for performing track positioning of the optical disc irradiated with the laser beam based on the track error signal.
An optical pickup position detection unit for detecting a light spot position from a rotation center on the disk to a light spot;
A pulse generation unit that generates a multiplied pulse signal based on a pulse signal generated by a rotation angle reference position detector that detects a rotation angle reference position of a spindle motor that rotates the optical disc;
A rotation angle detector that detects the rotation angle position of the optical disc by counting the number of pulses from the reference position of the multiplied pulse signal;
Based on a reference clock, a rotational speed detector that detects the rotational speed of the optical disc from the multiplied pulse signal;
A track error signal period detector for detecting a period of the track error signal at the rotation angle generated when the light spot crosses a plurality of tracks when the light spot is fixed at a predetermined position on the optical disc;
A minimum cycle angle position detector that obtains the rotation angle position in a minimum cycle among the cycles of the track error signal corresponding to the rotation angle based on the number of pulses counted by the rotation angle detector;
An eccentricity calculation unit that calculates an eccentricity amount of the optical disc based on a minimum cycle of the track error signal detected by the track error signal cycle detection unit and a rotation speed of the optical disc detected by the rotation speed detection unit When,
Correction gain setting means for correcting the amplitude of the track error signal at the rotation angle position of the optical disk and the light spot position based on the amount of eccentricity of the optical disk and the rotation angle position of the optical disk at which the track error signal obtains the minimum period; An optical disc recording / reproducing apparatus comprising:

Images