JPH07114019B2 - Track error signal detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track error signal detecting device for use in an optical disk device or the like for performing servo control in tracking by pulling in a wide range.

[0002]

2. Description of the Related Art Conventionally, an optical pickup used in an optical disk device irradiates a track, which is a pit train of recorded information on an optical disk, with a laser beam or the like, and the reflected light is, for example,
The light is incident on the divided light receiving elements. The difference in division of the reflected light spots over the two divided light receiving elements is detected as a track error signal. On the basis of this track error signal, servo control is performed so that the laser light applied to the track of the optical disc is made to follow the optical system of the optical pickup so as not to deviate from the track, so-called tracking is performed. Is always read accurately.

FIG. 5 is a block diagram showing the structure of a conventional track error signal detecting device. In FIG. 5, this apparatus includes an optical pickup 2 of an optical system that reads out the track of recorded information on an optical disc D, and a track error detector 3 that is a split-type photodetector provided in the optical pickup 2. Have Further, the apparatus is provided with an error detection signal amplifier 4 which generates, amplifies and outputs a track error detection signal S1 which is a difference between two output signals from the track error detector 3.

The operation of the conventional track error signal detecting device will be described below. Split type track error detector 3 provided in the optical pickup 2
The track error detection signal S1, which is the difference between the two output signals from, is generated by the error detection signal amplifier 4 and is amplified and output.

The track error detection signal S1 is generated by the spot center of the laser light emitted from the optical pickup 2 when the optical pickup 2 moves in the direction traversing the track of the optical disc D, for example, when the optical disc D is eccentrically rotated. Is a substantially sine waveform in which the track position shown in FIG. The track error detection signal S1 having the sine waveform shown in FIG. 6 is supplied to a servo control circuit and a drive mechanism (not shown), and tracking is performed so that the optical system of the optical pickup 2 always follows the track position in FIG.

[0006]

In such a conventional track error signal detecting device, servo control is performed so that the spot center of the laser beam applied to the track of the optical disk D is located at the track center position shown in FIG. That is, tracking is performed.

In such a servo operation, there is a range in which the servo control for aligning the center of the laser beam spot from the optical pickup 2 with the track center position is possible. That is, the track error detection signal S shown in FIG.
1 is limited to the pull-in range of the maximum waveform value of the sine waveform. Therefore, when the laser light emitted from the optical pickup 2 is emitted to the position between the tracks, the track error detection signal S1 deviates from the maximum waveform of the sine waveform shown in FIG. In this case, since the track error detection signal S1 having a sufficient level cannot be obtained, stable servo control cannot be performed.

The following proposals have been made regarding this type of track error signal detecting device.

(1) In the "track crossing signal detection device" disclosed in Japanese Patent Laid-Open No. 59-195343, a signal indicating the amount of reflected light from the disk is sampled at the rising and falling points of the track error signal. , The sampling point and the number of tracks across the track can be accurately detected.

(2) In the "readout signal correction device for a disk device" disclosed in Japanese Patent Laid-Open No. 61-034769, the amplitude fluctuation amount of the RF signal is detected from at least one of the tracking error signal and the focus error signal. The sum of the corresponding voltage and the average voltage of the RF signal is used as the binarization level voltage of the RF signal to enable stable signal reproduction at all times.

(3) In the "tracking balance measuring device" disclosed in Japanese Patent Laid-Open No. 1-106376, the offset deviation is calculated based on the detection of the level inversion interval of the binary signal of the tracking error of the disk device. ing.
The offset deviation of the tracking servo is automatically measured to improve the manufacturing efficiency of the disk device.

[0012] (4) In the disclosed in Japanese Patent Laid-Open No. 2-015427 "tracking error detection method", by detecting the width of a pulse corresponding to a more pair of wobble pits on the optical detector, these pulses widths A stable tracking error signal with little gain variation is calculated based on this difference. In these examples, there is room for improvement in tracking control from the viewpoint of expanding the pull-in range.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a track error signal detecting device capable of widening a pull-in range in tracking control and reading track record information on various recording media.

[0014]

SUMMARY OF THE INVENTION In the present invention corresponding to this object, track error detection is performed to detect a track error difference signal which is a difference between at least two output signals obtained by optically reading a track of an information recording medium. and means, door
Two signals, the maximum and minimum rack error difference signals, are predicted.
The signal storage means that has been stored for
At least two output signals obtained by optical reading
The maximum and minimum values stored in this signal storage means based on
Binary signal generating means for selecting one of the values to generate a binarized signal, and reading the track of the information recording medium from at least two output signals obtained by optically reading the track of the information recording medium. Depending on the track position detecting means for detecting either the track position or between the two tracks and the track position or the two tracks detected by the track position detecting means, a track error difference signal or a binary value from the track error detecting means. And a selecting means for selecting and outputting the binarized signal from the digitized signal generating means.

[0015]

Further, the track position detecting means includes a sum signal storage means for storing in advance the average level of the sum signal of at least two output signals obtained by optically reading the tracks of the information recording medium, and the sum signal storage means. The level of the sum signal from the information recording medium and at least two output signals obtained by optically reading the track of the information recording medium are compared, and the reading of the track of the information recording medium is performed at the track position or between the two tracks. This is a configuration including a comparison / determination means for determining either.

[0017]

In the invention having such a structure, the difference between the track errors is
The maximum value and the minimum value of the signal are stored in the signal storage means respectively.
Any one of these is selected by the binarized signal generation means.
A binary signal that takes a value is generated. Then, the reading of the track is detected at the track position or between the two tracks. By this detection, the track error difference signal or the binarized signal from the binarized signal generating means is selected and output. For example, the optical pickup also pulls Write-out of range incapable of servo control across the tracks, the output track error detection signal retractable obtained. Therefore, the pull-in range in the tracking control is widened, and the track record information can be read on various storage media. Also, the binarized signal is
The maximum or minimum value of the error signal
Even when switching between the rack error difference signal and the binarized signal
These do not become discontinuous. This allows you to switch
It is possible to improve the stability of the servo control.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the track error signal detecting apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a track error signal detecting device of the present invention. In FIG. 1, the apparatus of the present embodiment includes an optical pickup 12 for reading recorded information by tracking following a track on an optical disc D,
The optical pickup 12 is provided with a track error detector 13 (corresponding to track error detecting means in the claims) which is a split type photodetector.

Further, the apparatus includes an error detection amplifier 14 which generates and amplifies and outputs a track error detection signal S2 which is a difference between two output signals from the track error detector 13, and the track error detector 13. 2 of the output signals are compared and the positive and negative track error binarization signals S3 are output according to the level of the two.
A binarization circuit 15 (corresponding to the binarized signal generation means in the claims) and a sum signal level detection circuit 16 for outputting a sum signal S4 which is the sum of two output signals from the track error detector 13 (claims). Corresponding to the track position detecting means).

Further, in this device, the track error detection signal S2 from the error detection amplifier 14 or the track error binarization signal S3 from the binarization circuit 15 is added to the sum signal S.
Output track error detection signal S5 selected based on 4
And a changeover switch 17 (corresponding to the selecting means in the claims). The changeover switch 17 has a fixed terminal 17a to which the track error detection signal S2 is supplied, a fixed terminal 17b to which the track error binarization signal S3 is supplied, and a movable terminal for selecting either the fixed terminal 17a or the fixed terminal 17b. The contact point 17c.

These configurations can be easily configured by using a conventional operational amplifier or comparator.

The operation of the track error signal detecting device having the above structure will be described below. FIG. 2 is a signal waveform diagram of each part when the optical pickup 12 moves in a direction crossing the track of the optical disc D, for example, when the optical disc D is eccentrically rotated. In FIG. 2, the optical pickup 1
When 2 moves across the track of the optical disc D, two output signals from the track error detector 13 are input to the error detection amplifier 14. Then, the error detection amplifier 14 outputs the track error detection signal S2 shown in FIG. The track error detection signal S2 is supplied to the fixed terminal 17a of the changeover switch 17.

The two output signals from the track error detector 13 are also input to the binarization circuit 15 together with the error detection amplifier 14. The binarization circuit 15 compares the levels of the two output signals from the track error detector 13 and outputs the positive and negative track error binarized signals S3 shown in FIG. To do.

Further, the two output signals from the track error detector 13 are input to the sum signal level detection circuit 16. The sum signal level detection circuit 16 is the sum of the two output signals from the track error detector 13 (d) in FIG.
The sum signal S4 shown in is obtained. If the sum signal S4 to the optical pickup 12 is <br/> moves in a direction crossing the track of the optical disk D, a waveform waveform and phase of the track error detection signal S2 shown in FIGS. 2 (a) is shifted 90 degrees Become. That is, the laser light emitted from the optical pickup 12 reaches the maximum level at the track center position of the optical disc D,
The laser light emitted from the optical pickup 12 has a low level at a position between two tracks in the optical disc D.

The sum signal level detection circuit 16 uses the threshold value m of the average value shown by the dotted line in the sum signal S4 in FIG. 2 (d) as a threshold, and at a level higher than the threshold value m, the track error detection signal S2. The movable contact 17c selects the fixed terminal 17a of the changeover switch 17 supplied with the sum signal S4. At a level lower than the threshold value m, the movable contact 17c outputs the sum signal S4 for selecting the fixed terminal 17b of the changeover switch 17 to which the track error binarization signal S3 is supplied.

That is, in the pull-in range in which the track error detection signal S2 shown in FIG. 2A can be pulled from the track center position, the track error detection signal S2 shown in FIG. It is output as an output track error detection signal S5 through the terminal 17a and the movable contact 17c. Further, in the case where the laser light radiated from the optical pickup 12 to the track of the optical disc D deviates from the maximum waveform of the sine waveform radiated to the position between the tracks, the pull-in is impossible.
The fixed terminal 17b and the movable contact 17c of the changeover switch 17 for the track error binarized signal S3 shown in the middle (b).
Is output as an output track error detection signal S5.

Therefore, the output track error detection signal that can be pulled in even outside the pull-in range where the servo control for aligning the centers of the laser light spots is impossible as in the previous description in which the optical pickup 12 crosses the track of the optical disc D. Since S5 is obtained, it becomes possible for the servo control circuit and drive mechanism (not shown) to always follow the optical system of the optical pickup 12 to the track position.

Next, the detailed configuration and operation of the binarization circuit 15 will be described. FIG. 3 is a block diagram showing a detailed configuration of the binarization circuit 15. In FIG. 3, the binarization circuit 15 stores a binary signal of positive polarity or negative polarity corresponding to the maximum value and the minimum value of the two output signals from the track error detector 13 and stores the stored positive electrode. Difference signal storage circuit 20 which outputs a negative polarity signal or a negative polarity signal, respectively
(Corresponding to the signal storage means in the claims).

Further, the binarization circuit 15 has a changeover switch 21 for selecting the positive or negative polarity signal from the difference signal storage circuit 20. The changeover switch 21 includes a fixed terminal 21a and a fixed terminal 21b to which a positive or negative signal from the difference signal storage circuit 20 is respectively supplied, and a movable contact 21c for selecting the fixed terminal 21a or the fixed terminal 21b. .

The binarizing circuit 15 has a movable contact 21 of a changeover switch 21 based on the positive or negative polarity of the two output signals from the track error detector 13.
An output selection circuit 22 that outputs a drive signal for switching c is provided. The configuration of the changeover switch 21 and the output selection circuit 22 corresponds to the output selection means in the claims.

The binarizing circuit 15 of this configuration corresponds to the maximum value and the minimum value of the two output signals from the track error detector 13 when the optical pickup 12 is moved in the direction traversing the track of the optical disk D in advance. The positive or negative binary signal is stored in advance. That is, the fixed terminal 2 of the switch 21 switches the positive or negative signal in the binarized signal converted corresponding to the maximum value and the minimum value of the two output signals from the track error detector 13.
1a and the fixed terminal 21b, respectively. In this supply state, the output selection circuit 22 outputs a drive signal for switching the movable contact 21c of the changeover switch 21 based on the positive polarity or the negative polarity of the two output signals from the track error detector 13.

This switching is performed by the track error detector 1
When one of the two output signals from 3 has a positive polarity, a drive signal for selecting the fixed terminal 21a is output to the movable contact 21c. As a result, the positive polarity signal in the track error binarized signal S3 shown in FIG.
Is output from. When the other of the two output signals from the track error detector 13 has a negative polarity, the movable contact 21
A drive signal for selecting the fixed terminal 21b is output to c. As a result, a negative polarity signal in the track error binarization signal S3 shown in FIG. 2B is output from the movable contact 21c, and this operation continues, whereby the track error binarization shown in FIG. The signal S3 is obtained.

Here, a positive polarity or a negative polarity corresponding to the maximum value and the minimum value of the two output signals from the track error detector 13 when the optical pickup 12 is previously moved in the direction traversing the track of the optical disc D. Although the binary signal is stored, a positive or negative binary signal having an appropriate level may be stored in advance.

Next, the detailed structure and operation of the sum signal level detection circuit 16 will be described. FIG. 4 is a block diagram showing a detailed configuration of the sum signal level detection circuit 16. In FIG. 4, the sum signal level detection circuit 16 stores the average level of the sum signal of the two output signals from the track error detector 13 in advance (a sum signal storage circuit 26 (corresponding to sum signal storage means in the claims). )have.

Further, this sum signal level detection circuit 16
Compares the average level of the track sum signal from the sum signal storage circuit 26 with the levels of the two output signals from the track error detector 13 so that the laser light spot from the optical pickup 12 is located at the track position or between the two tracks. And a comparison circuit 28 (corresponding to the comparison / determination means in the claims) for determining the position and outputting the sum signal S4.

In the sum signal level detection circuit 16 of this structure, the average level track sum signal from the sum signal storage circuit 26 and the levels of the two output signals from the track error detector 13 are compared by the comparison circuit 28. Optical pickup 1
The laser light spot from 2 outputs the sum signal S4 of (d) in FIG. 2 which indicates the track position or the position between two tracks.

With the configuration of the binarization circuit 15 and the sum signal level detection circuit 16 as described above, the track error detector 13 is provided.
It is possible to store a positive or negative binary signal corresponding to the maximum value and the minimum value of the two output signals from, and to store the average level of the track sum signal in advance. Therefore, the stored value can be changed to support various discs.

[0038]

As is apparent from the above description, according to the present invention, the maximum value and the minimum value of the track error difference signal are set separately.
Stored in the signal storage means and stored in the binarized signal generation means.
A binary signal that takes one of these values is generated.
It Then, the reading of the track is detected at the track position or between the two tracks. By this detection, the track error difference signal or the binary signal from the binarized signal generating means
The digitized signal is selected and output. For example, an optical pickup crosses a track and pulls in when servo control is impossible.
Also seen outside the scope retraction because the obtained output track error detection signal as possible be broadly capture range is in the tracking control has the effect that it is possible to read the track recording the information in a wide variety of recording media. The binarized signal is the maximum value of the track error difference signal.
Or, since it takes the minimum value, the track error difference signal and 2
These should not be discontinuous even when the digitized signal is switched.
Yes. This ensures stable servo control during switching.
It is possible to improve the sex.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a track error signal detection device of the present invention.

FIG. 2 is a signal waveform diagram of each part in the operation of the embodiment.

3 is a block diagram showing a detailed configuration of a binarizing circuit in FIG.

FIG. 4 is a block diagram showing a detailed configuration of a sum signal level detection circuit in FIG.

FIG. 5 is a block diagram showing a configuration of a conventional track error signal detection device.

6 is a waveform diagram showing a waveform of a track error detection signal in the configuration shown in FIG.

[Explanation of symbols]

 12 optical pickup 13 track error detector 14 error detection amplifier 15 binarization circuit 16 sum signal level detection circuit 17, 21 changeover switch 20 difference signal storage circuit 22 output selection circuit 26 sum signal storage circuit 28 comparison circuit

Claims (2)

[Claims] 1. A track error detecting means for detecting a track error difference signal which is a difference between at least two output signals obtained by optically reading a track of an information recording medium, and a maximum value and a minimum value of the track error difference signal. Two beliefs of value
Signal storage means for storing the signal in advance, and the signal storage means based on at least two output signals obtained by optically reading the tracks of the information recording medium.
Select either the maximum or minimum value stored in
Binary signal generating means for generating a binarized signal, and reading the track of the information recording medium from at least two output signals obtained by optically reading the track of the information recording medium is at a track position or between two tracks. Depending on the track position detecting means for detecting any of the above and the track position detected by the track position detecting means or between the two tracks, the track error difference signal from the track error detecting means or the binarized signal generating means A track error signal detecting device, comprising: a selecting unit that selects and outputs a binarized signal. 2. The track position detecting means includes a sum signal storage means for storing in advance an average level of sum signals of at least two output signals obtained by optically reading a track of an information recording medium, and the sum signal storage means. The level of the sum signal from the information recording medium and at least two output signals obtained by optically reading the track of the information recording medium are compared, and the reading of the track of the information recording medium is performed at the track position or between the two tracks. 2. The track error signal detecting device according to claim 1, further comprising a comparing / judging means for judging either of them.