JP2849072B2 - Spindle servo circuit of optical disk playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle servo for an optical disk reproducing apparatus for an optical disk having a synchronization mark for obtaining a synchronization signal for reading data and a data field for a mark indicating data on each track. Circuit.

[0002]

2. Description of the Related Art For example, in an optical disk having a recording format of a sampled servo system, a synchronization pattern composed of two marks (pits) is formed on a track of a servo field in order to obtain a synchronization signal for reading recorded data. The distance between the two marks is longer than the maximum inversion interval, which is the maximum distance between marks in a mark portion indicating data. For example, it is longer than the maximum inversion interval by 1T (T is 1 bit interval). At the time of disc reproduction (playback), first, a reading operation is performed while a servo system is operated by an asynchronous master clock pulse, and a synchronous pattern is detected from a read signal. After the detection of the synchronization pattern, a clock mark is detected from the read signal, and a clock pulse is generated from the PLL circuit in synchronization with the clock mark. When the PLL circuit reaches a locked state, the reproduced clock pulse for data reading becomes P
Obtained from LL circuit.

A CAV (Constant Angul) having a constant rotation speed
In the case of an ar Velocity type optical disk, after the rotation speed reaches a constant speed, the synchronization pattern can be easily detected from its length, so the clock pulse must be reproduced from the read signal as described above. Can be.

[0004]

However, in the case of a CLV type optical disk having a constant linear velocity, the rotational speed of the spindle is not constant, so that the synchronous pattern cannot be easily detected from its length. Therefore, the maximum inversion interval portion is detected by counting the master clock pulse, and spindle servo control is performed so that the maximum inversion interval portion has a predetermined time length. Assuming that the maximum inversion interval kT in the data is kT and the length of the synchronization pattern is (k + 1) T, when the synchronization pattern is to be detected using a master clock pulse of twice the frequency, the length of the synchronization pattern is asynchronous. (K + 1) T ± including the error due to the master clock pulse
0.5T. If the rotation error of the spindle is 0.5T or more, the count value of the synchronous pattern by the master clock pulse can be kT. Therefore, CLV
In the case of the optical disk of the type, there is a problem that it is difficult to easily detect the synchronization pattern separately from the maximum inversion interval in the data.

Accordingly, an object of the present invention is to provide an optical disc and a spindle servo circuit of an optical disc reproducing apparatus capable of easily detecting a synchronization pattern even in the case of a CLV type discrimination from a maximum inversion interval in data. is there.

[0006]

[0007]

[0008]

The spindle servo circuit of the reproducing apparatus of the present invention, in order to solve the problems] comprises a synchronization mark for obtaining a synchronizing signal for data read and a data field for the mark indicating the data in each track, A mark indicating the data, wherein T is a 1-bit interval of the data, nT (n is an integer) the length of the synchronization mark in the track direction, and αT is a detection error generated when the synchronization mark is read and detected. Is the maximum inversion interval of mT (m is an integer),

[0009]

(N−α) T> mT where α ≧ 2

[0010]

## EQU8 ## A spindle servo circuit of an optical disk reproducing apparatus in which an integer n is set so as to satisfy the following two expressions: mT × (n + α) / n <nT, wherein the optical disk is optically read by a pickup. Reversal interval detecting means for binarizing the read signal and detecting a reversal interval indicating a synchronization signal from the binarized read signal;
A spindle control signal generating unit for generating a spindle control signal based on an output of the inversion interval detecting unit and a reference value indicating a predetermined time length; and a driving unit for driving a spindle motor according to the spindle control signal. It is characterized by.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIGS. 1A and 1B show servo fields of a double-density recording CLV type optical disk as an embodiment of the present invention. In this optical disk, each track is formed at an interval of, for example, 0.4 μm. As shown in FIGS. 1 (a) and 1 (b), the sample field of each track has a synchronous pit having a length of 11T (T is 1 bit interval) at the beginning, and then a plurality of pits for tracking servo. Are formed. The pit width of the synchronous pit is, for example, 0.2 μm. In each servo field of the odd track, as shown in FIG. 1 (a), a first tracking pit having a length of 4T and being separated from the trailing edge of the synchronous pit by 15T from the track center toward the end direction of the segment. A clock pit that is located on the left side as a wobble pit and that is 13T away from the trailing edge of the first tracking pit and has a length of 4T is located on the track. Further, a second tracking pit having a length of 4T, which is 13T away from the trailing edge of the track pit, is located as a wobble pit on the right side of the track center in the segment end direction. In each servo field of the even track, as shown in FIG.
A first tracking pit having a length of T is located as a wobble pit on the left side of the track center in the direction of the end of the segment, and a clock pit having a length of 4T on the track at a distance of 13T from the trailing edge of the first tracking pit. Located in. Further, a second tracking pit having a length of 4T, which is 13T away from the trailing edge of the clock pit, is located as a wobble pit on the right side of the track center in the segment end direction. The wobble pit is formed at a position away from the track center by, for example, 0.2 μm. A data field (not shown) is located after such a servo field.

FIG. 2 shows a clock pulse generation circuit for generating a clock pulse for controlling data reproduction timing from a read signal of the optical disk having the servo field shown in FIG. In this clock pulse generation circuit, a light beam for reading information is irradiated from the pickup 11 to the disk, and an RF (high frequency) signal which is a read signal read from the disk by the pickup 11 is A / D-converted.
It is supplied to a converter 12. The RF signal is supplied to the A / D converter 12
Are supplied to a clock pit phase detector 13, a threshold calculator 14, and an edge interval / synchronization detector 15. The clock pit phase detector 13 obtains a phase error signal indicating a difference between sample values before and after the clock pit waveform from the digital RF signal according to the clock sampling signal. The PLL circuit 16 is connected to the clock pit phase detection unit 13,
The LL circuit 16 generates a reproduced clock pulse and supplies it to the changeover switch 19 to control the phase or frequency of the reproduced clock pulse according to a phase error signal or a frequency control signal described later. The changeover switch 19 selectively outputs a reproduced clock pulse and a master clock pulse output from the PLL circuit 16 in accordance with a first frequency lock signal described later. The master clock pulse is generated from a pulse generator (not shown). The clock pulse selected and output from the changeover switch 19 is supplied to the A / D converter 12, the edge interval / synchronization detection unit 15, and the timing generation unit 17.

[0013] The threshold calculation unit 14 is a digital R
Detecting the positive and negative peak levels of the F signal at predetermined intervals,
An intermediate value between the positive and negative peak levels is calculated as a threshold level. The edge interval / synchronization detecting section 15 detects the digital RF signal exceeding the threshold level by counting the clock pulse from the changeover switch 19 when the digital RF signal exceeds the threshold level. When the count value of the clock pulse is equal to or more than the first predetermined value, the synchronization is performed. A synchronization detection signal indicating pit detection is generated.

A timing generator 17 and a frequency error generator 18 are connected to the edge interval / synchronization detector 15. The timing generator 17 counts the clock pulses from the changeover switch 19 based on the time when the synchronization detection signal is generated to generate the clock sampling signal, and converts the clock sampling signal to the clock pit phase detector 13.
To supply. The frequency error generation unit 18 calculates the synchronization signal generation interval from the synchronization detection signal by counting the reproduction clock pulse from the PLL circuit 16, and compares the count value of the reproduction clock pulse with a second predetermined value. A frequency control signal is generated accordingly. The frequency control signal is P
The frequency of the reproduced clock pulse is supplied to the LL circuit 16 and controlled in accordance with the frequency control signal. The frequency error generator 18 generates a first frequency lock signal when the frequency of the reproduced clock pulse falls within a first predetermined range, and generates a first frequency lock signal when the frequency of the recovered clock pulse falls within a second predetermined range narrower than the first predetermined range. 2
Generate a frequency lock signal. The first frequency lock signal is supplied to the changeover switch 19, and the second frequency lock signal is supplied to the PLL circuit 16.

In the clock pulse generation circuit having such a configuration, in the initial state, the changeover switch 19 selectively outputs the master clock pulse. Therefore, the A / D converter 1 converts the RF signal read from the disk by the pickup 1
2 obtains a sample value in response to the master clock pulse and digitizes it. An intermediate value between the positive and negative peak levels of the digital RF signal is calculated as the threshold level by the threshold calculation unit 14. When a digital RF signal exceeding the threshold level is detected, the excess time is obtained in the edge interval / synchronization detecting section 15 by counting the master clock pulse.

The edge interval / synchronization detector 15 generates a synchronization detection signal when the count value of the master clock pulse is equal to or greater than a first predetermined value. The master clock pulse is counted based on the occurrence of the synchronization detection signal, and a clock sampling signal indicating the clock pit reading time is generated in the timing generator 17 and the clock pit phase detector 1
3 is supplied. The clock pit phase detector 13 obtains a phase error signal indicating a difference between sample values before and after the clock pit waveform from the digital RF signal according to the clock sampling signal.

The reproduced clock pulse generated from the PLL circuit 16 is supplied to a frequency error generator 18, and the synchronization signal generation interval is obtained from the synchronization detection signal by counting the reproduced clock pulse. The count value of the clock pulse is compared with a second predetermined value, and a frequency control signal is generated according to the comparison result. In the initial state, the frequency control signal controls the frequency of the reproduced clock pulse of the PLL circuit 16 and is in a frequency control loop state. The frequency error generator 18 generates a first frequency lock signal when the frequency of the reproduced clock pulse falls within a first predetermined range.
In response to the first frequency lock signal, the changeover switch 19
The reproduced clock pulse output from the L circuit 16 is A / D
The signal is relay-supplied to the converter 12, the edge interval / synchronization detector 15, and the timing generator 17. Therefore, the A / D converter 1
2. The edge interval / synchronization detection unit 15 and the timing generation unit 17 operate according to the reproduced clock pulse instead of the master clock pulse.

The accuracy of the frequency of the reproduced clock pulse controlled by the frequency control signal increases as a plurality of synchronization signals are detected. When the frequency of the recovered clock pulse falls within a second predetermined range, a second frequency lock signal is generated. In response to the second frequency lock signal, the PLL circuit 16 controls the phase of the recovered clock pulse in response to the phase error signal from the clock pit phase detector 13 instead of the frequency control signal, and the clock pulse generation circuit operates in the phase control loop state. Becomes

FIG. 3 shows a spindle servo circuit for controlling the rotation speed of the optical disk of FIG. In this spindle servo circuit, a threshold calculator 21 and an edge interval detector 22 are connected to the output of the A / D converter 12. The threshold calculator 21 detects the positive and negative peak levels of the digital RF signal output from the A / D converter 12 at predetermined intervals, and calculates an intermediate value between the positive and negative peak levels as the threshold level. When detecting the digital RF signal exceeding the threshold level, the edge interval detecting section 22 obtains the time when the digital RF signal exceeds the threshold level by counting the number of input clock pulses from the changeover switch 19 of the clock pulse generation circuit. The output of the edge interval detection unit 22 is connected to a synchronization detection unit 23 and a maximum inversion interval hold unit 24. The synchronization detection unit 23 generates a synchronization detection signal when the count value of the clock pulse obtained by the edge interval detection unit 22 is equal to or greater than a first predetermined value. The maximum inversion interval holding unit 24 holds the maximum value of the count values of the input clock pulses obtained by the edge interval detection unit 22 as the maximum inversion interval. Maximum inversion interval hold unit 24
Is reset by the timer 25. The timer 25 measures a time longer than the period in which the synchronous pit is read during the reproduction of the optical disk. When the timer 25 measures the time, it generates a reset signal and repeats the time measuring operation. The first comparison operation unit 26 is connected to the maximum inversion interval holding unit 24. The first comparison operation unit 26 includes a maximum inversion interval hold unit 24
Is compared with the reference value, and an error signal is output. The reference value is a synchronization pit length 11T.

The output error signal of the first comparison operation section 26 is supplied to a changeover switch 27 and a first spindle lock detection section 28. The first spindle lock detector 28 generates an enable signal when the level of the output error signal of the first comparison calculator 26 is within a third predetermined range, and supplies the enable signal to the changeover switch 27 and the synchronization protection unit 29. The synchronization protection unit 29 outputs the synchronization detection signal generated by the synchronization detection unit 23 when the enable signal exists. When the enable signal is not present, a pulse signal is output at each synchronization signal generation interval according to the input clock pulse. The synchronization interval measurement unit 30 is connected to the synchronization protection unit 29. The synchronization interval measuring unit 30 counts the generation interval of the output signal of the synchronization protection unit 29 according to the clock pulse, and supplies it to the second comparison operation unit 31. The second comparison operation unit 31 compares the count value of the input clock pulse of the synchronization interval measurement unit 30 with a reference value, and outputs an error signal. This reference value corresponds to a count value when the spindle motor is rotating at a regular speed. The output of the second comparison operation unit 31 is connected to a second spindle lock detection unit 32 together with the changeover switch 27. Second spindle lock detector 3
2 indicates that the level of the output error signal of the second comparison
A spindle lock flag is generated when the value is within a predetermined range.

The switch 27 relays the output signal of the first comparison / calculation unit 26 as a spindle control signal when the enable signal is not present, and uses the output signal of the second comparison / calculation unit 31 as the spindle control signal when the enable signal is present. Relay output. The relay output of the changeover switch 27 is D /
It is supplied to a drive circuit 34 of a spindle motor (not shown) via an A converter 33.

Although the threshold calculator 21 is provided separately, the threshold calculator 14 shown in FIG. 2 may be used. Further, the edge interval detection unit 22 and the synchronization detection unit 2
3 can also use the edge interval / synchronization detector 15 of FIG. In the spindle servo circuit having such a configuration, since the input clock pulse is supplied from the above-described clock pulse generation circuit, the operation of generating the spindle control signal is performed in the initial state according to the master clock pulse. That is, the A / D converter 12 obtains a sample value according to the master clock pulse from the RF signal read from the disk by the pickup 11, and digitizes the sample value. The intermediate value between the positive and negative peak levels of the digital RF signal is calculated as the threshold level by the threshold calculation unit 21. When a digital RF signal exceeding the threshold level is detected, the excess time is obtained in the edge interval detecting section 22 by counting the master clock pulses. The synchronization detector 23 generates a synchronization detection signal when the count value of the master clock pulse is equal to or greater than a first predetermined value.

The count value of the master clock pulse obtained in the edge interval detection section 22 is used as the maximum inversion interval hold section 24.
Is held. Since the edge interval detecting unit 22 sequentially outputs the count value of the master clock pulse, if the present value of the count value of the master clock pulse is larger than the value held in the maximum inversion interval holding unit 24, the current value is set to the maximum inversion interval. It is newly held in the holding unit 24. The value held by the maximum inversion interval holding unit 24 and the reference value are compared in the first comparison / calculation unit 26, and the error is supplied to the D / A converter 33 via the changeover switch 27 as a spindle control signal. The drive circuit 34 drives the spindle motor in accordance with the analogized spindle control signal.

When the level of the spindle control signal from the first comparison operation section 26 is within the third predetermined range, the first spindle lock detection section 28 generates an enable signal. When the enable signal is generated, the changeover switch 27 relays the output signal of the second operation / comparison unit 31 and sets the synchronization protection unit 2
Reference numeral 9 outputs the synchronization detection signal generated by the synchronization detection unit 23 to the synchronization interval measurement unit 30. The synchronization interval measuring unit 30 counts the generation interval of the output signal of the synchronization protection unit 29 according to the input clock pulse, the count value of the input clock pulse and the reference value are compared in the second comparison operation unit 31, and the error signal is calculated. Is output. The output error of the second comparison / calculation unit 31 is supplied to the D / D
It is supplied to the A converter 33. The drive circuit 34 drives the spindle motor in accordance with the analogized spindle control signal.

When the level of the spindle control signal output from the second comparison operation section 31 is within a fourth predetermined range, a second spindle lock detection section 32 generates a spindle lock flag. The spindle lock flag is supplied to a system controller (not shown) of the disc player, so that the fact that the rotation of the spindle motor is normally controlled is transmitted.

In the clock pulse generation circuit, a PLL
When the frequency of the reproduced clock pulse of the circuit 16 falls within the first predetermined range and the first frequency lock signal is generated, the reproduced clock pulse output from the PLL circuit 16 replaces the master clock pulse with the input clock pulse. As supplied to the spindle servo circuit. Therefore, the A / D converter 12, the edge interval detection unit 22, the synchronization detection unit 23, the synchronization protection unit 29, and the synchronization interval measurement unit 30 operate according to the reproduced clock pulse. Even when the input clock pulse is replaced with the recovered clock pulse, the first comparison operation unit 26 does not exist when the enable signal is absent, as in the above operation.
The spindle control signal from the D /
The spindle control signal from the second comparison operation unit 31 is supplied to the D / A converter 33 via the switch 27 when the enable signal is supplied to the A converter 33.

As described above, in the initial state, the detection of the synchronization signal interval is performed by the master clock pulse. Therefore, assuming that the synchronization signal interval is nT, the detection accuracy is (n ± 1) T even with the correct synchronization signal interval. . Therefore, the interval between the synchronization signals at the rotation accuracy at the time of coarse spindle control according to the spindle control signal from the first comparison / calculation unit 26 is (n ± 2) T in consideration of the rotation variation ± 1T of the control error. It is estimated to be. Therefore, when the rotation speed of the CLV type optical disk is high, in order to be able to distinguish between the synchronous pit and the maximum inversion interval mT of data, in the case of mT = 8T,

[0028]

## EQU9 ## The condition (n-2) T> 8T is required. On the other hand, when the rotation speed of the optical disk is low, the maximum data inversion interval 8T must not be mistaken for a synchronous pit.

[0029]

## EQU10 ## The condition 8T × (n + 2) / n <nT must be satisfied. The minimum integer n that satisfies both equations is 11, and the synchronous pit length is 11T. In the above example, the maximum inversion interval mT is 8T, and the detection error that occurs when a synchronous pit is read and detected as a synchronous signal is 2T, and the present invention is not limited to these values.

When detecting the maximum reversal interval of the recording mark from the read signal for detecting the synchronization mark, the detection interval is set longer than the appearance interval of the synchronization mark when the rotation speed of the disk is minimum.

[0031]

As described above, according to the present invention, in an optical disc having, on each track, a synchronization mark for obtaining a synchronization signal for reading data and a data field for a mark indicating data, one of data is recorded. The bit interval is T, the length of the synchronization mark in the track direction is nT, and the detection error that occurs when the synchronization mark is read and detected is α.
T, and the maximum mark reversal interval for data is mT
Then, (n−α) T> mT and mT × (n + α) /
Since n is set so as to satisfy the two expressions of n <nT, the length of the synchronization mark can be set in consideration of the detection error and the change in the number of revolutions of the disk. Therefore, even in the case of a CLV-type optical disk, the synchronization pattern can be accurately distinguished from the maximum inversion interval in the data and detected.

In the spindle servo circuit of the optical disk reproducing apparatus, an inversion interval value indicating a synchronization signal detected from a binary read signal from the optical disk;
Since the spindle control signal is generated based on the reference value indicating the predetermined time length, the spindle rotation control can be performed without mistaken for the synchronization pit and the maximum inversion interval mT of data.

[Brief description of the drawings]

1 is a diagram showing a servo field of the optical disc.

FIG. 2 is a block diagram illustrating a clock pulse generation circuit.

FIG. 3 is a block diagram showing a spindle servo circuit according to the present invention .

[Description of Signs of Main Parts]

 Reference Signs List 11 pickup 13 clock pit phase detector 14, 21 threshold calculator 15 edge interval / synchronization detector 16 PLL circuit 17 timing generator 18 frequency error generator 22 edge interval detector 23 synchronization detector 24 maximum inversion interval hold unit 30 synchronization Interval measurement unit

Claims (1)

(57) [Claims] 1. Each track is provided with a synchronization mark for obtaining a synchronization signal for data reading and a data field for a mark indicating data, and a bit interval of the data is T, and a track of the synchronization mark is provided. The length in the direction is nT
(N is an integer), a detection error generated when reading and detecting the synchronization mark is αT, and a maximum reversal interval of the mark indicating the data is mT (m is an integer). α) T> mT, where α ≧ 2. A spindle servo circuit of an optical disk reproducing apparatus in which an integer n is set so as to satisfy two expressions of mT × (n + α) / n <nT. Inversion interval detection means for binarizing a read signal from the optical disc obtained by being read and detecting an inversion interval indicating the synchronization signal from the binarized read signal, and an output of the inversion interval detection means A spindle control signal generating means for generating a spindle control signal based on the reference value indicating the predetermined time length; and a drive for driving a spindle motor according to the spindle control signal. Spindle servo circuit comprising: the means.