JPH0540948A - Tracking control device - Google Patents

Abstract

PURPOSE:To accurately discriminate the moving direction of an optical head by adjusting the gain of a variable means so that the output difference of a first and second converting means may be made the same in both areas where rugged bits are recorded and not recorded. CONSTITUTION:A focusing servo is turned on, and sum signals S2 and the output of a variable gain amplifier 18 S21 are varied in a sinusoidal waveform. Then, S21 is converted to a digital value by means of an AD converter 25, monitored by a CPU19, and S21max and S21min are determined. This value is taken in the CPU19, calculated and made a RF signal amplitude. In this case, RF signal S10 receives a signal regeneration through a binarization circuit. By replacing the set value of a gain variable amplifier 23 with a specified formula, the optimum RF signal is obtained. When the sum signal S21 and an envelope detection signal S11 are added, a sinusoidal wave from which the influence of bits is eliminated is obtained; and by binarizing it, an accurately reflected pulse signal is obtained inspite of a ROM area and a sector head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device for an information recording / reproducing head used in an optical disk device or the like.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed as a tracking control method for optical disks. Among them, the push-pull method that uses a four-division sensor is common. FIG. 7 shows a block diagram of a circuit for generating a tracking signal and a focusing error signal using the push-pull method. In the figure, 1 is a four-division sensor that receives the light reflected from the optical disk, and 2 is a sensor amplifier that amplifies the output of each sensor. This sensor amplifier 2
The tracking error signal S1 is generated as a result of performing an analog operation on the output of 1 using the adders 3 and 4 and the subtracter 5. As shown in FIG. 8A, the tracking error signal S1 is 0 on-track and one track has a sinusoidal waveform of one cycle. The point A shown in FIG. 8 will be described later. Further, the adder 6 outputs a signal reflecting the total amount of light received by the four-division sensor 1, that is, a sum signal S2. The sum signal S2 is also track 1 as shown in FIG.
Although the waveform is close to a sine wave with one cycle of the book, it is maximum in on-track (on-land) and minimum in on-group, so the phase is 90 degrees out of phase with the tracking error signal S1. The sum signal S2 is binarized by comparing the average level of each output of the peak hold circuit 11 and the bottom hold circuit 12 obtained by the average value output circuit 13 with the comparator 14. FIG. 8B also shows the output S3 of the peak hold circuit 11, the output S4 of the bottom hold circuit 12, and the output S5 of the average value output circuit 13. Average value output circuit 1
The output S5 of 3 is compared with the sum signal S2 by the comparator 14 as described above, and binarized into a pulse signal S6 as shown in FIG.

On the other hand, the tracking error signal S1 is output to the comparator 10, where it is compared with a zero level to obtain a pulse signal S7 as shown in FIG. 8 (c).
Valued. In this case, the outputs S6 and S7 of the comparators 10 and 14 respectively reflect the phases of the tracking error signal and the sum signal, and thus the phases are deviated by 90 degrees. Therefore, by performing the phase comparison between S6 and S7 using the phase comparator 15, it is possible to determine the relative movement direction of the optical head with respect to the optical disc. Further, the relative position of the optical head with respect to the optical disc can be known by counting up / down the binarized output S7 based on the direction-determined signal. The focusing error signal obtained by the astigmatism method includes the adders 7 and 8 and the subtractor 9.
Is generated as an output S9 by performing an analog operation using.

[0004]

However, the conventional tracking control device is effective for an optical disc in which only the guide groove of the track is carved, but uneven pits are recorded on a part or all of the disc. If so, an error may occur in binarizing the sum signal. Hereinafter, this problem will be described in detail. In a general optical disc, a track is divided into several sectors in the circumferential direction, and data is managed in sector units. However, at the beginning of each sector, data for disc management, such as track address and sector address, is written. Data is recorded. These are called sector headers, and are generally recorded in concave and convex pits. Some optical discs, such as ROM discs or partial ROM discs, have data in all or part of the disc area recorded with concave-convex pits and are read-only. As an example, the waveform of each part in the vicinity of the boundary between the rewritable area (MO area) and the read-only area (ROM area) of the partial ROM disk will be described with reference to FIG.

The waveform of FIG. 8 shows the waveform of each part when the optical head moves from the MO area to the ROM area while traversing the track. In the figure, point A represents the boundary between the MO area and the ROM area. Sector header and R in MO area
In the OM region, the amplitude of the push-pull signal becomes small as shown in FIG. 8A because the reflectance of the disk is lowered due to the influence of the uneven pits. However, since the point that crosses the zero level does not change, it is not affected by the binarized signal S7. However, the sum signal is D in the MO area and the ROM area.
Since the C level changes and the way the signal is disturbed in the sector header portion is large, it is greatly affected by the binarized signal S6. That is, the binarization level of the sum signal is peak hold,
Since the average level of the bottom hold is used, the binarization level cannot quickly follow when the optical head moves from the MO area to the ROM area or passes through the sector header. Therefore, there is a problem in that the binarization of the sum signal is erroneous and the direction cannot be discriminated well.

The present invention has been made in order to solve such a problem, and tracking control is performed so that the moving direction of the optical head can be accurately discriminated even in a recording medium having concave and convex pits recorded therein. It is intended to provide a device.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to generate a tracking error signal and a sum signal from signals of a servo sensor of an optical head for recording or reproducing information on an optical information recording medium. By comparing the phases,
In a tracking control device for determining a relative movement direction of an optical head with respect to the recording medium, first conversion means for converting the level of the sum signal into a digital value, variable means for changing the magnitude of the sum signal, and Means for reading the information recorded in the recording medium by the concave and convex pits, means for envelope detection of the read signal, second conversion means for converting the detection output into a digital value, and the detection output as described above. Means for adding to the sum signal so that the difference between the output of the first conversion means and the difference between the output of the second conversion means in the area where the concave and convex pits are recorded and the area where the concave and convex pits are not recorded are substantially equal. In addition, it is achieved by a tracking control device characterized in that the gain of the variable means is adjusted.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the tracking control device of the present invention. Note that FIG.
The same parts as those of the conventional device are denoted by the same reference numerals, and detailed description thereof will be omitted in this embodiment. In FIG. 1, 19 is a CPU for automatically adjusting the sum signal level, and 20 is a CPU
A DA converter for analog-converting the output of 19 and an adder 17 for adding the output of the DA converter 20 to the sum signal. Further, 18 is a variable gain amplifier that changes the gain of the sum signal, 21 is an RF sensor for reading the RF signal modulated by the concave and convex pits, 22 is a preamplifier for appropriately amplifying the sensor output, and 23 is RF. It is a variable gain amplifier that adjusts the amplitude of a signal. Further, 24 is an envelope detection circuit for envelope detection of the RF signal, 25,
Reference numeral 26 is an AD converter for converting the sum signal and the envelope detection output into a digital value, and 27 is a timing circuit for giving a conversion timing to each AD converter.

FIG. 2 is a waveform diagram showing signals of respective parts when the tracking servo is turned on in the MO area of the disk. FIG. 2A shows the tracking error signal S1, which is almost 0 because the tracking servo is on. FIG. 2B shows the sum signal S2, which is almost constant at a certain positive level, but at the sector header portion, the reflectivity of the disk is lowered due to the influence of the uneven pits, and therefore the level is lowered. On the other hand, FIG. 2 (c) shows the envelope detection signal S11, in which the AC signal appears in the RF signal for reproducing the concave and convex pits at the sector header, and therefore the envelope detection output level is raised. Therefore, in the present invention, both of them are added after level adjustment to cancel the influence of the concave and convex pits, whereby a position signal accurately reflecting the relative position of the optical disk and the optical head is obtained.

The specific operation of this embodiment will be described with reference to the flow chart shown in FIG. In FIG.
First, the CPU 19 determines whether or not an optical disc has been inserted into the device (step 1), and when the insertion of the optical disc is confirmed, the gain G1 of the variable gain amplifier 18 is set to G10,
The gain G2 of the variable gain amplifier 23 is set to G20, and the set value D of the DA converter 20 is set to DO (step 2). Then, the focusing servo is turned on (step 3), and at this time, the eccentricity of the disk causes the light spot of the optical head to cross several tracks, so that the sum signal S2
Also, the output S21 of the variable gain amplifier 18 changes in a sine wave shape. Therefore, the AD converter 25 is used to convert S21 into a digital value, which is monitored by the CPU 19, and S2
1 _max and S21 _min are obtained (step 4). At this time,
The AD conversion cycle is set shorter than the minimum period in which the non-recorded portion continues in the circumferential direction (determined by the format of the disk and even existing in the ROM disk), so that the maximum value and the minimum value of the sum signal in the MO area are set. You can know the value. The set value D of the DA converter 20 is reset from the value obtained here by the following equation (step 5).

D = DO- (S21 _max + S21 _min ) / 2 (1) As a result, the DC level of the input of the variable gain amplifier becomes close to 0, so that the dynamic range of the variable gain amplifier can be increased. ..

Thereafter, the tracking servo is turned on (step 6). The waveform of each part when the tracking servo is on is as shown in FIG. 2, and FIG. 2 (a) shows the tracking error signal, which is almost 0 because the servo is on.
FIG. 2B shows a sum signal, and the level is lowered in the sector header portion due to the influence of pits. On the contrary, since the preamplifier output outputs an AC signal in accordance with the pit, the envelope detection signal S11 has a raised level in the sector header portion as shown in FIG. 2 (c). At this point, the timing signal generating circuit 27 is activated to generate clock pulses in the sync signal portion and the non-recording portion in the sector header as shown in FIG. 2 (d). The rising edge of the clock in the non-recording section is T1, the rising edge in the synchronizing signal section is T2, and the envelope detection signal S11 is converted into digital values S111 and S112 by the AD converter 26 at the timing of T1 and T2 (step 7).
The CPU 19 fetches this value and sets S112-S111.
Is calculated as the RF signal amplitude. In this case, the RF signal S
Generally, 10 reproduces a signal through a not-shown differentiating circuit and a binarizing circuit. At this time, it is desirable to adjust the RF signal amplitude to a level most convenient for the signal reproduction. For example, the optimum RF signal amplitude for the signal reproduction system is X
Then, the optimum RF signal can be obtained by replacing the set value of the variable gain amplifier 23 with the following equation (step 8).

G2 = G20.X / (S112-S111) (2) Next, the sum signal S21 is similarly AD-converted at the timing of T1 and T2 to obtain data S211 and S212 (step 9). Therefore, if the set value of the variable gain amplifier 18 is replaced with the following equation, the modulation degree that the sum signal S21 receives by the pits is just X (step 10).

G1 = G10 · X / (S211−S212) (3) The modulation by the pit is reversed between the sum signal and the envelope detection signal even when the tracking servo is off. Therefore, after the adjustment up to this point is completed, the sum signal and the envelope detection signal are overlapped to solve the above-mentioned problems, and then the sum signal 2
The value can be accurately converted.

FIG. 4 is a diagram showing the signal waveform of each part after the above adjustment. FIG. 4A shows the tracking error signal S1.
FIG. 4B shows the sum signal S2. Further, FIG. 4C shows the adjusted sum signal S21, the DC level in the MO region is close to 0, and the drop of the sum signal in the sector header portion becomes X on track. In this figure, the sector header is located at a position slightly off from the on-track, so it is slightly smaller than X. Also, ROM
In the area, the on-group is not so much affected by the pits, so the level is almost the same as in the MO area, and in the on-land, the level is lowered because it is greatly affected. On the other hand, FIG. 4D shows the RF signal S10 and the envelope detection signal S11 superimposed on each other. In the ROM area, the influence of the pits is also large on land, so that the envelope detection signal S11 becomes a sine wave having the same phase as the sum signal S2 and the amplitude X.
In the MO area, a pulsed signal can be obtained only in the sector header section. Therefore, when the sum signal S21 and the envelope detection signal S11 are added together, as shown in FIG. 4 (e), it is possible to obtain a sine wave having a shape excluding the influence of pits. Therefore, if this is binarized, RO as shown in FIG.
It is possible to obtain a pulse signal accurately reflecting the land and the groove regardless of the M region and the sector header.

Although the AD timing signal has been described as generating two pulses in the non-recording area and the synchronizing signal area in the above embodiments, if the AD conversion is performed at the timings of T1 and T2, It goes without saying that it does not depend on the waveform of the timing signal. Further, if the gain variable amplifier 18 has a sufficient dynamic range, there is no problem even if the order of the adder 17 is changed.

FIG. 5 is a block diagram showing another embodiment of the present invention. This embodiment is suitable when the dynamic range of the reproduction circuit system of the RF signal is wide and no gain adjustment is necessary, and the variable gain amplifier 23 of the RF signal is unnecessary. In this case, the gain is adjusted with the RF signal using the variable gain amplifier 18 for the sum signal.
Automatic adjustment is performed by the algorithm shown in. In FIG.
After starting the timing circuit with the tracking servo turned on, S13 and S21 are AD at the timing of T1 and T2.
Convert (steps 7 and 8). Next, the conversion data are set to S91, S92, S211, and S212, respectively, and the set value of the variable gain amplifier is changed to the following equation (step 9).

G1 = G10. (S92-S91) / (S211-S212) (4) By performing the above setting, the same effect as that of the above-described embodiment can be obtained.

[0019]

As described above, according to the present invention, the gain of the sum signal and the RF signal is adjusted when the recording medium is inserted so as to cancel the influence of the pits. The sum signal can be binarized without removing the adverse effect of the header. Therefore,
Even in a recording medium in which uneven pits are recorded, there is an effect that the relative movement direction of the optical head with respect to the recording medium can be accurately determined regardless of the recording medium.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a tracking control device of the present invention.

FIG. 2 is a waveform diagram showing signal waveforms of respective parts when the tracking servo is turned on in the MO region in the embodiment of FIG.

FIG. 3 is a flowchart showing a level adjustment operation of a sum signal according to the embodiment of FIG.

FIG. 4 is a time chart showing signal waveforms of respective parts after level adjustment in the embodiment of FIG.

FIG. 5 is a block diagram showing another embodiment of the present invention.

FIG. 6 is a flowchart showing a level adjusting operation of the sum signal according to the embodiment of FIG.

FIG. 7 is a block diagram showing a conventional tracking control device.

FIG. 8 is a time chart showing signal waveforms of respective parts of the conventional device.

[Explanation of symbols]

 1 4-division sensor 3, 4, 17, 28 Adder 15 Phase comparator 18, 23 Variable gain amplifier 19 CPU 20 DA converter 21 RF sensor 24 Envelope detection circuit 25, 26 AD converter

Claims (1)

[Claims] 1. A recording error medium and a sum signal are generated from a signal of a servo sensor of an optical head which records or reproduces information on an optical information recording medium, and the phases of these two signals are compared with each other, thereby recording the recording medium. In a tracking control device that determines the relative movement direction of the optical head with respect to the first recording medium, first conversion means for converting the level of the sum signal into a digital value, variable means for changing the magnitude of the sum signal, and the recording medium. Means for reading the information recorded in the uneven pits, means for envelope detection of the read signal,
Second conversion means for converting the detected output into a digital value,
Means for adding the detected output to the sum signal, and a difference between an output of the first converting means and an output of the second converting means in an area where the concave and convex pits are recorded and an area where the concave and convex pits are not recorded. The tracking control device is characterized in that the gain of the variable means is adjusted so that