JP3833372B2 - Mirror signal generating apparatus and information reproducing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a mirror signal indicating the timing of closing a tracking servo loop after moving a light spot across a plurality of information tracks when reproducing information recorded on a disk-shaped recording medium such as an optical disk. Belongs to the technical field of a mirror signal generation device for generating
[0002]
[Prior art]
Conventionally, when information on the disk-shaped recording medium is optically reproduced, the focal position of the light beam used for the reproduction is matched with the position of an information track formed on the disk-shaped recording medium by the information. Therefore, so-called tracking servo control and so-called focus servo control for matching the focal position with the position of the information recording surface of the disk-shaped recording medium are indispensable.
[0003]
On the other hand, when reproducing information, a so-called track jump operation or seek operation is performed in which the focal position is moved across a plurality of information tracks to a position on a disc-shaped recording medium on which desired information is recorded. Sometimes. During the track jump operation, the tracking servo loop in the tracking servo control is opened, and the tracking servo loop is switched to the closed state when the focal position is positioned on the desired information track. Tracking servo control needs to be restarted.
[0004]
For this reason, conventionally, a reproduction signal detected when performing a track jump operation or the like (reproduction RF (corresponding to information to be reproduced detected based on reflected light from the disk-shaped recording medium of the light beam) ( (Radio Frequency) signal), the focus position of the light beam is “HIGH” when it is on the information track, and “LOW” when it is in a region other than the information track (region sandwiched between adjacent information tracks). The mirror signal is generated, the relationship between the focal position and the information track position is grasped using the mirror signal, and the tracking servo loop is switched to the closed state.
[0005]
More specifically, a tracking error detection signal generated in parallel based on the reflected light during the track jump operation or the like (from “LOW” to “HIGH” at the center of an area sandwiched between adjacent information tracks). And the mirror signal are compared with each other on the central axis of the information track, and the mirror signal is “HIGH” on the desired information track. The tracking servo loop is switched from the open state to the closed state at the timing when the tracking error detection signal is switched from “HIGH” to “LOW”.
[0006]
In this way, tracking servo control can be resumed by accurately closing the tracking servo loop when the focal position is on the information track.
[0007]
Here, in the generation of the mirror signal, conventionally, a constant voltage value obtained by dividing the maximum amplitude value of the reproduction RF signal generated when the tracking servo loop is in an open state before reproduction of information by a predetermined voltage division ratio. (Specifically, a reference slice signal having a voltage value level matching the center level of the lower envelope signal of the reproduction RF signal when the tracking servo loop before information reproduction is in an open state) A reproduction RF signal detected during a track jump operation during information reproduction is compared, and when the value of the reproduction RF signal is higher than the level of the reference slice signal, the value of the reproduction RF signal is the reference. The mirror signal is generated so as to be “LOW” when it is lower than the level of the slice signal. At this time, the level of the reference slice signal was always constant during the reproduction of information.
[0008]
[Problems to be solved by the invention]
However, according to the mirror signal generation method as described above, the level of the reference slice signal is higher than the maximum value of the lower envelope of the reproduction RF signal due to a change in the modulation degree of the reproduction RF signal during reproduction. There is a problem that the level becomes high or, on the contrary, the level becomes lower than the minimum value of the lower envelope, and as a result, a binary signal as a mirror signal may not be obtained.
[0009]
That is, in the disk-shaped recording medium, generally, the modulation degree of the reproduction RF signal (corresponding to the amplitude of the lower envelope of the reproduction RF signal) when the tracking servo loop is in an open state (that is, during the track jump operation or the like). ) May differ between the inner periphery and the outer periphery of the disc-shaped recording medium. This state appears remarkably in a high-density recording medium such as a DVD that has been generalized in recent years (an optical disc having a storage capacity increased to about 7 times that of a conventional CD (Compact Disk)). If the modulation degree changes as described above, the mirror signal itself as the binarized signal cannot be generated as described above.
[0010]
Therefore, the present invention has been made in view of the above-mentioned problems, and the problem is that the mirror signal can be accurately generated even if the modulation degree of the reproduction RF signal changes when the tracking servo loop is open. It is an object of the present invention to provide a mirror signal generation device capable of performing the above and an information reproduction device including the mirror signal generation device.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problem, the invention described in claim 1 is a mirror signal generation device included in an information reproduction device that reproduces information using a light beam, and includes a focal position of the light beam and the information. Mirror signal indicating whether or not the focal position is on the information track when the tracking servo loop for matching the position of the information track formed on a recording medium such as an optical disk is in an open state A pickup that generates a reproduction signal corresponding to the information based on the reflected light of the light beam from the recording medium when the tracking servo loop is in an open state bottle for detecting the lower envelope, generating a first lower envelope signal corresponding in the generation unit and the generated reproduction signal A first lower envelope signal generating means such as a detection circuit, and averages the first lower envelope signal said generated averaging means such LPF (Low Pass Filter) for generating an averaged signal, the reproduction signal An upper envelope signal generating means such as a peak detecting circuit for detecting an upper envelope in the first lower envelope signal, and detecting a lower envelope in the first lower envelope signal, and a corresponding second lower envelope signal A second lower envelope signal generating means such as a bottom detection circuit for generating a value obtained by subtracting the value of the generated second lower envelope signal from the value of the generated averaged signal. Storage means such as an arithmetic circuit for storing a value obtained by dividing a value of the second lower envelope signal by a value obtained by subtracting the value of the second envelope signal from the value of the upper envelope signal Multiplying the stored value by a value obtained by subtracting the value of the second lower envelope signal generated during reproduction of the information from the value of the upper envelope signal generated during reproduction of the information; Slice signal generation means such as an arithmetic circuit for generating a slice signal having a value obtained by adding the values of the second lower envelope signal generated during reproduction of the information, the generated slice signal, and the first lower signal It compares the lateral envelope signal, characterized in that it comprises a comparison generation means such as a comparator for generating the mirror signal.
[0012]
In order to solve the above problem, the invention according to claim 2 is the mirror signal generation device according to claim 1, wherein at least the averaged signal is generated before reproduction of the information. .
[0015]
In order to solve the above-mentioned problem, the invention described in claim 3 is the mirror signal generation device according to claim 1 or 2 , and control means for closing the tracking servo loop based on the mirror signal, And reproducing means for reproducing the information based on the reproduction signal after the tracking servo loop is closed.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Next, preferred embodiments of the present invention will be described with reference to the drawings. The embodiment described below is an embodiment when the present invention is applied to an information reproducing apparatus that reproduces information recorded on an optical disc as a recording medium.
[0038]
First, the overall configuration and operation of the information reproducing apparatus according to the embodiment will be described with reference to FIG.
[0039]
As shown in FIG. 1, an information reproducing apparatus S according to the embodiment includes an optical disc 1, a pickup 2 as a generating means, a reproducing section 3 as a reproducing means, and a mirror signal as a mirror signal generating apparatus according to the present invention. The generator 4 includes a tracking error signal generator 5, a focus error signal generator 6, a servo processor 7 as control means, and a spindle motor 8.
[0040]
Next, the operation will be described.
[0041]
At the time of information reproduction, the optical disk 1 is rotated at a predetermined rotational speed by a spindle motor 8 driven by a spindle control signal Ssd described later.
[0042]
Then, the pickup 2 emits a light beam B such as a laser beam to the rotating optical disc 1, and generates a reproduction RF signal Srf corresponding to information on the optical disc 1 to be reproduced based on the reflected light.
[0043]
In parallel with this, the pickup 2 generates a focus error detection signal Sfp indicating the deviation of the focal position of the light beam B from the information recording surface of the optical disc 1 based on the reflected light, and based on the reflected light. Thus, a tracking error detection signal Stp is generated which indicates a deviation in the direction parallel to the information recording surface (tracking direction) between the position of the information track formed on the optical disc 1 and the focal position of the light beam B by the information to be reproduced. To do.
[0044]
Next, the mirror signal generation unit 4 performs the operation described later using the reproduction RF signal Srf output from the pickup 2 during the track jump operation or seek operation (that is, when the tracking servo loop is open). During the track jump operation or seek, when the focal position of the light beam B is on the information track formed by information on the optical disc 1, it becomes “HIGH”, and when it is in an area other than the position of the information track, it is “LOW”. Is generated and output to the servo processing unit 7.
[0045]
In parallel with this, the reproduction unit 3 performs a demodulation process or the like on the reproduction RF signal Srf when the track jump operation or the seek operation is not performed, and outputs the reproduction signal Sp corresponding to the information to be reproduced to the outside. Output to.
[0046]
On the other hand, the tracking error signal generator 5 to which the tracking error signal Stp is input generates a tracking error signal Ste indicating the deviation of the tracking direction of the light beam B based on the tracking error detection signal Stp, and performs servo processing. Output to unit 7.
[0047]
In parallel with this, the focus error signal generator 6 to which the focus error detection signal Sfp is input shifts the focal position of the light beam B from the position of the information recording surface based on the focus error detection signal Sfp. Is generated and output to the servo processing unit 7.
[0048]
Accordingly, the servo processing unit 7 first drives an objective lens (not shown) included in the pickup 2 in the tracking direction based on the tracking error signal Ste when the track jump operation or the seek operation is not performed. Is output to a tracking actuator (not shown) in the pickup 2 (a tracking actuator for moving the objective lens in the tracking direction).
[0049]
In parallel with this, the servo processor 7 drives a focus drive signal Sfd for driving an objective lens (not shown) included in the pickup 2 in a direction perpendicular to the information recording surface based on the focus error signal Sfe. Is output to a focus actuator (not shown) in the pickup 2 (a focus actuator for moving the objective lens in a direction perpendicular to the information recording surface).
[0050]
Then, when the tracking actuator and the focus actuator are driven based on the tracking drive signal Std and the focus drive signal Sfd, the objective lens moves in the tracking direction and the direction perpendicular to the information recording surface to reproduce information. Accordingly, so-called tracking servo control and focus servo control are executed.
[0051]
The servo processing unit 7 generates a spindle control signal Ssd for driving the spindle motor 8 based on the reproduction RF signal Srf, and outputs the spindle control signal Ssd to the spindle motor 8.
[0052]
On the other hand, at the time of the track jump operation or seek operation, the servo processing unit 7 counts the number of tracks that perform track jump operation or seek operation using the input tracking error signal Ste and mirror signal Smr. Next, slip brake detection and the like during so-called pull-in operation in tracking servo control are performed. Next, the configuration and operation of the mirror signal generation unit 4 according to the present invention will be described with reference to FIGS.
[0053]
As shown in FIG. 2, the mirror signal generation unit 4 includes a peak detection circuit 10 as an upper envelope signal generation unit, a bottom detection circuit 11 as a lower envelope signal generation unit and a first lower envelope signal generation unit, The bottom detection circuit 13 as the second lower envelope signal generation means, the LPF 12 as the averaging means, and the mirror signal generation circuit 14 are configured.
[0054]
Further, the mirror signal generation circuit 14 includes an arithmetic circuit 15 as slice signal generation means and a comparator 16 as comparison generation means.
[0055]
Next, the operation of each unit will be described.
[0056]
First, the operation of the mirror signal generation unit 4 when the tracking servo loop is in an open state before reproducing information from the optical disk 1 will be described.
[0057]
When the irradiation position of the light beam B moves across the information track due to the eccentricity of the optical disk 1 or the like when the tracking servo loop is in the open state, for example, it has a waveform as shown in FIG. A reproduction RF signal Srf is output from the pickup 2. At this time, the waveform of the lower envelope of the reproduction RF signal Srf corresponds to the presence or absence of an information track. That is, the period in which the value of the lower envelope is higher than the center level indicates the timing when the irradiation range of the light beam B is on an area other than the information track, and the value of the lower envelope is lower than the center level. The period indicates the timing when the irradiation range of the light beam B is on the information track.
[0058]
When the reproduction RF signal Srf having such a waveform is input to the peak detection circuit 10 when the tracking servo loop is open, the peak detection circuit 10 detects the upper envelope of the reproduction RF signal Srf, A corresponding envelope signal Spe (see FIG. 3B) is generated and output to the arithmetic circuit 15 in the mirror signal generator 14.
[0059]
In parallel with this, the bottom detection circuit 11 to which the reproduction RF signal Srf is input detects the lower envelope of the reproduction RF signal Srf and generates a corresponding envelope signal Sbe (see FIG. 3B). Output to the LPF 12 and the bottom detection circuit 13.
[0060]
Next, the LPF 12 averages the input envelope signal Sbe with a predetermined time constant set in advance (which is of course shorter than the period during which the tracking servo loop is open), and FIG. An averaged signal Sav as shown in (c) is generated and output to the arithmetic circuit 15.
[0061]
On the other hand, the bottom detection circuit 13 detects the lower envelope of the input envelope signal Sbe, generates an envelope signal Sbbe as shown in FIG.
[0062]
Then, the arithmetic circuit 15 uses each of the envelope signal Spe, the envelope signal Sbbe, and the averaged signal Sav that are input.
[Expression 1]
Vs = {(level of averaged signal Sav) − (level of envelope signal Sbbe)} / {(level of envelope signal Spe) − (level of envelope signal Sbbe)}
Is calculated and is temporarily stored in the arithmetic circuit 15.
[0063]
Next, the operation of the mirror signal generation unit 4 when a track jump operation or a seek operation is executed during actual information reproduction will be described.
[0064]
The reproduction RF signal Srf output from the pickup 2 when the irradiation position of the light beam B moves across the information track during the track jump operation or seek operation is obtained when the tracking servo loop described above is open. It has a waveform similar to that of the reproduction RF signal Srf, for example, as shown in FIG. Even at this time, the period in which the value of the lower envelope of the reproduction RF signal Srf is higher than the center level indicates the timing at which the irradiation range of the light beam B is on an area other than the information track. The period when the value is lower than the center level indicates the timing when the irradiation range of the light beam B is on the information track.
[0065]
Next, the peak detection circuit 10 detects the upper envelope of the reproduction RF signal Srf at the time of the track jump operation or seek operation, and generates a corresponding envelope signal Spe (see FIG. 3B) to generate a mirror signal. To the arithmetic circuit 15 in the unit 14.
[0066]
In parallel with this, the bottom detection circuit 11 to which the reproduction RF signal Srf is inputted detects its lower envelope, generates a corresponding envelope signal Sbe (see FIG. 3B), and generates a bottom detection circuit. 13 and the comparator 16.
[0067]
Next, the bottom detection circuit 13 detects the lower envelope of the input envelope signal Sbe, generates an envelope signal Sbbe as shown in FIG.
[0068]
The arithmetic circuit 15 uses the envelope signal Spe and the envelope signal Sbbe that are input and the level Vs stored in the arithmetic circuit 15, respectively.
[Expression 2]
Vss = {(level of envelope signal Spe) − (level of envelope signal Sbbe)} × Vs + (level of envelope signal Sbbe)
Is generated and output to the comparator 16.
[0069]
Thereafter, the comparator 16 compares the level of the input envelope signal Sbe with the level Vss of the slice signal Ss to generate a mirror signal Smr that is a binary signal having a waveform shown in FIG. And output to the tracking error signal generator 5.
[0070]
Thereafter, as soon as the track jump operation or seek operation is completed, the servo processing unit 7 closes the tracking servo loop based on the mirror signal Smr and the tracking error signal Ste output during the track jump operation or seek operation. The tracking servo control is resumed by detecting the timing to perform, and the generation of the tracking drive signal Std is resumed.
[0071]
As described above, according to the operation of the information reproducing apparatus S of the embodiment, the level Vss generated based on the envelope signal Spe, the envelope signal Sbbe, and the averaged signal Sav is compared with the envelope signal Sbe to obtain a binary value. Since the mirror signal Smr, which is a signal to be converted, is generated, the mirror signal Smr having a waveform that accurately corresponds to the relationship between the focal position of the light beam B and the position of the information track even if the modulation degree of the reproduction RF signal Srf changes. Can be generated. Therefore, by using the mirror signal Smr, the tracking servo loop can be shifted to the closed state at an accurate timing.
[0072]
Therefore, even when the tracking servo loop is opened and a track jump or the like occurs when the modulation degree of the reproduction RF signal Srf changes, information can be accurately reproduced.
[0073]
Since the value obtained by subtracting the value of the envelope signal Sbbe from the value of the average signal Sav and the value obtained by subtracting the value of the lower envelope signal Sbbe from the value of the envelope signal Spe is the level Vs, the envelope A slice signal Ss having a level within the amplitude range of the signal Sbe can be reliably generated, and a mirror signal Smr having a waveform that accurately corresponds to the relationship between the focal position of the light beam B and the position of the information track is generated. Can do.
[0074]
Furthermore, the averaged signal Sav is generated when the tracking servo loop at the beginning of information reproduction is open, and the light beam B crosses the information track during the information reproduction using the generated averaged signal Sav. Since the mirror signal Smr is generated on the basis of the slice signal Ss generated at the same time, the time during which the light beam B crosses the information track during the reproduction of information (that is, the time during which the tracking servo loop is open) is short, and the envelope The mirror signal Smr can be generated accurately even if there is no time for averaging the signal Sbe.
[0075]
In the embodiment described above, the level Vs is calculated and stored in the arithmetic circuit 15 when the tracking servo loop before information reproduction is in an open state. When the servo loop is in an open state, only the averaged signal Sav is generated and the level is stored in the arithmetic circuit 15, and then the averaged signal Sav every time the track jump operation or seek operation during information reproduction is performed. The level Vs may be calculated using the current level and the envelope signal Spe and the envelope signal Sbbe input at that time, and the mirror signal Smr may be generated based on the level Vs.
[0076]
Further, when the tracking servo loop before the information reproduction or the like is in an open state, the average signal Sav and the envelope signal Sbbe are used,
[Equation 3]
Vsss = (level of averaged signal Sav) − (level of envelope signal Sbbe)
Is calculated and stored in the arithmetic circuit 15 to generate a slice signal Ss having a level obtained by adding the level of the envelope signal Sbbe to the level Vsss during a track jump operation or a seek operation during information reproduction. You may make it do.
[0077]
Further, regarding the calculation of the level Vsss, only the level of the averaged signal Sav is calculated when the tracking servo loop before the information reproduction or the like is in an open state, and every time the track jump operation or seek operation is performed during the information reproduction. The level Vsss may be calculated using the level of the average signal Sav and the level of the envelope signal Sbbe detected at that time.
[0078]
Furthermore, when the track jump operation or seek operation is executed for a long period during information reproduction, the averaged signal Sav itself is calculated for each track jump operation or seek operation, and is used as described above. The mirror signal Smr may be calculated by processing.
[0079]
According to the information reproducing apparatus S, the focal position of the light beam B is accurately grasped and the tracking servo loop is closed to reproduce the information. Therefore, when the modulation degree of the reproduction RF signal Srf changes, the tracking servo loop is opened. Even if a track jump or the like occurs, information can be accurately reproduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an information reproducing apparatus.
FIG. 2 is a block diagram showing a schematic configuration of a mirror signal generation unit.
FIGS. 3A and 3B are diagrams illustrating a generation operation of a mirror signal, where FIG. 3A is a diagram illustrating a waveform example of a generated reproduction RF signal, and FIG. 3B is a diagram illustrating a waveform of each envelope of the reproduction RF signal; (C) is a figure explaining the production | generation of an average signal, (d) is a figure explaining the production | generation of a mirror signal.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Pickup 3 ... Playback part 4 ... Mirror signal generation part 5 ... Tracking error signal generation part 6 ... Focus error signal generation part 7 ... Servo processing part 8 ... Spindle motor 10 ... Peak detection circuit 11, 13 ... Bottom Detection circuit 12 ... LPF
14 ... mirror signal generation circuit 15 ... arithmetic circuit 16 ... comparator S ... information reproduction device B ... light beam Srf ... reproduction RF signal Sp ... reproduction signal Stp ... tracking error detection signal Sfp ... focus error detection signal Smr ... mirror signal Ste ... tracking Error signal Sfe ... Focus error signal Std ... Tracking drive signal Ssd ... Spindle control signal Sfd ... Focus drive signal Spe, Sbe, Sbbe ... Envelope signal Sav ... Average signal Ss ... Slice signal

Claims (3)

A mirror signal generation device included in an information reproduction device for reproducing information using a light beam, in order to match the focal position of the light beam with the position of an information track formed on a recording medium by the information In a mirror signal generation device for generating a mirror signal indicating whether or not the focal position is on the information track when the tracking servo loop is open,
Generating means for generating a reproduction signal corresponding to the information based on reflected light from the recording medium of the light beam when the tracking servo loop is in an open state;
First lower envelope signal generating means for detecting a lower envelope in the generated reproduction signal and generating a corresponding first lower envelope signal;
Averaging means for averaging the generated first lower envelope signal and generating an averaged signal;
Upper envelope signal generating means for detecting an upper envelope in the reproduction signal and generating a corresponding upper envelope signal;
Second lower envelope signal generating means for detecting a lower envelope in the first lower envelope signal and generating a corresponding second lower envelope signal;
A value obtained by subtracting the value of the generated second lower envelope signal from the value of the generated average signal, and a value of the second lower envelope signal subtracted from the value of the generated upper envelope signal. Storage means for storing the value divided by the value;
Multiplying the stored value by a value obtained by subtracting a value of the second lower envelope signal generated during reproduction of the information from a value of the upper envelope signal generated during reproduction of the information; and Slice signal generating means for generating a slice signal having a value obtained by adding a value of the second lower envelope signal generated during reproduction of information;
Comparison generating means for comparing the generated slice signal with the first lower envelope signal and generating the mirror signal;
A mirror signal generation device comprising: The mirror signal generation device according to claim 1,
At least the averaged signal is generated before the information is reproduced. The mirror signal generation device according to claim 1 or 2 ,
Control means for closing the tracking servo loop based on the mirror signal;
Reproduction means for reproducing the information based on the reproduction signal after the tracking servo loop is closed;
An information reproducing apparatus comprising:

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