JP2002150696A - Reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To considerably reduce the circuit scale of a rough servo circuit to reduce the cost and the power consumption and to improve the reliability of a system. SOLUTION: With respect to a rotation servo circuit, the frequency in inversion of an inputted EFM signal is detected (21 and 22). The circuit is so constituted that this frequency may be compared with a prescribed reference value (23) by a means (24) to generate a rotation servo signal as rough servo. The reference value is determined on the basis of an average frequency in inversion of all generated patterns of the EFM signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for a disk-shaped recording medium, and more particularly to a rotary servo circuit mounted on the reproducing apparatus.

[0002]

2. Description of the Related Art Systems using disks such as CDs (compact disks) and MDs (mini disks) as recording media have become widespread. In these systems, EF, a kind of run-length limited code, is used for PCM data.
Data subjected to M modulation (8-14 modulation) is recorded on a disk. In addition, a CLV (constant linear velocity) method is employed for rotating the disk.

For CLV rotation servo, a clock is reproduced by injecting an EFM signal read from a disk into a PLL circuit, and the clock is compared with a reference clock obtained by a crystal to obtain rotation error information. The rotation error information is fed back to a spindle motor that rotates the disk, so that a rotation state with a constant linear velocity can be obtained. In this specification, a servo circuit having such a configuration is referred to as a PLL servo circuit.

In order for such a PLL servo circuit to function, the PLL circuit must first be locked and a clock must be accurately extracted. For this reason, when starting up the spindle motor, the EF that is first extracted is
Rough servo control for drawing the M signal into the capture range of the PLL circuit is required. That is, in the normal disk reproducing apparatus, when starting the rotation of the spindle, first, a certain degree of rotation servo control is performed by the rough servo circuit,
Thereafter, when the PLL circuit is locked, the CLV servo operation is switched from the rough servo circuit to the PLL servo circuit.

FIG. 8 shows a configuration of a CLV servo system in a disk reproducing apparatus. 51 is a disk and 52 is a spindle motor. Reference numeral 53 denotes an optical head for reading data from the disk 51. The data read by the optical head 53 is output as an EFM signal via the RF amplifier 54. Although not shown, the reproducing system circuit is E
A reproduction signal such as audio data is obtained by performing EFM demodulation, error correction processing, and the like on the FM signal.

For the CLV servo system, the EFM signal is P
It is supplied to the LL servo circuit 55 and the rough servo circuit 60. As described above, the PLL servo circuit 50 reproduces a clock by injecting the EFM signal into the PLL circuit, and compares the clock with a reference clock obtained by a crystal to obtain rotation error information (rotation servo signal E _CLV-P ). It is configured as follows. The rotation servo signal E _CLV-P is the switching circuit 5
6 is supplied to the P terminal.

The rough servo circuit 60 detects a maximum or minimum inversion pattern included in the EFM signal, and obtains rotation error information (rotation servo signal E _CLV-S ) so that the pattern has an appropriate inversion interval / frequency. It is configured as follows. The rotation servo signal E _CLV-S is supplied to the S terminal of the switching circuit 56.

In the switching circuit 56, the S terminal is initially selected, so that the rotation servo signal E _{CLV- S} is supplied to the motor driver 57. Then, the motor driver 57 supplies drive power to the spindle motor 52 according to the rotation servo signal E _CLV-S . In the meantime, the PLL circuit is locked in the PLL servo circuit 55, but a lock detection signal Lock is output according to the lock of the PLL circuit, and the switching circuit 56 is locked.
Supplied to The switching circuit 56 connects the P terminal when the lock detection signal Lock is supplied, and thereafter, the motor driver 57
Supply the rotation servo signal E _CLV-P to the
The CLV servo by the operation of the L servo circuit 55 is executed.

Here, the rough servo circuit 60 is provided with an inversion interval measuring section 61, a peak hold circuit 62, a bottom hold circuit 63, and a magnitude comparator 64. The rotation servo signal E _CLV-S is operated by the following operation. generate.

An EFM signal extracted at a normal rotation speed in an MD system or a CD system is a reference clock T.
(T = 1 / 4.3218 MHz), and is composed of nine types of components having an inversion interval of 3T to 11T. Where E
At the beginning of one frame of the FM signal, the maximum inversion interval of 1
Two 1T patterns are encoded consecutively. FIG. 7 shows the configuration of one frame of the EFM signal. The first 24 bits of one frame of 588 bits are used as a sync pattern, and as shown in FIG.
T is a fixed pattern.

Subcode data, main data such as audio, and parity are arranged in 14 bits following the sync pattern as shown in the figure. 14
Three margin bits are arranged between each bit data. 3 as the main data in one frame
There are two symbols (one symbol = 14 bits), and for example, audio data is data of six sampling intervals for the L and R channels. Since 588 bits correspond to six sampling intervals, the frequency (RF clock) of one frame is 7.35 KHz. And above
4.3218MHz is the clock of each bit, that is, 7.35KH
It is a value of z × 588.

In the rough servo circuit 60, rough servo is performed by measuring a pattern width as a maximum inversion interval 11T seen in a sync pattern, for example. However, since there is a possibility that an inverted pattern of 11 T or more, which should be impossible due to a scratch on the disk, may be detected, a function of canceling such erroneous data is added.

In the rough servo circuit 60, the supplied EFM signal is first measured by a reversal interval measuring section 61. The measurement reference clock is 1 / T. The measured inversion interval is supplied to a peak hold circuit 62, for example, with a span of RF clock (7.35 KHz) / 2,
The value of the maximum inversion interval is held. The output of the peak hold circuit 62 is further supplied to a bottom hold circuit 63, for example, an RF clock (7.35 KHz) / 16
The value of the minimum inversion interval is held over a longer span. That is, the output of the bottom hold circuit 63 is the minimum inversion interval value among the maximum inversion interval values output from the peak hold circuit 62. That is, even if an inversion interval of 11 T or more occurs in the EFM signal due to a scratch on the disk or the like, these are canceled, and the inversion interval value in the correct 11T pattern is output from the bottom hold circuit 63.

The inversion interval value output from the bottom hold circuit 63 is supplied to a magnitude comparator 64. The magnitude comparator 64 is also supplied with the inversion interval value as the original 11T pattern, that is, the inversion interval value of the 11T pattern in the EFM signal extracted in the state of the normal rotation speed. Will be compared.
Then, the polarity and the absolute value obtained by the comparison processing, that is, error information are used as the rotation servo signal E _CLV-S .

[0015]

However, such a rough servo circuit 60 has a problem that the circuit scale becomes large, cost is increased, and power consumption is increased. That is, as described above, in order to prevent malfunction due to generation of an inversion interval of 11 T or more due to scratches and dirt on the disk, the maximum inversion interval value is detected within a certain time width (peak hold), It is necessary to adopt a method in which the minimum value is detected (bottom hold) within a wider time width and adopted as an appropriate maximum interval inversion pattern, which makes it difficult to reduce the circuit size. Because it is.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to remarkably reduce the circuit scale of a rough servo circuit.

For this purpose, the reproducing apparatus of the present invention comprises a rotating means for rotating the disk-shaped recording medium, a reproducing means for reproducing a modulation signal modulated by the EFM system, recorded on the disk-shaped recording medium, Inversion number measurement means for measuring the number of inversions of the modulation signal reproduced by the reproduction means, comparison means for comparing the inversion number measured by the inversion number measurement means with a reference value, and a comparison result of the comparison means And a control means for controlling rough servo rotation before the PLL is locked based on the reference value. The reference value compared by the comparison means is based on the average number of inversions of all the generation patterns of the modulation signal. It should be determined in advance.

The number of inversions of the EFM signal extracted from the disk is measured, and this is used as a reference value that should be, ie, EF.
The rotation error information can be obtained by comparing with a value determined in advance based on the average number of inversions of all the generation patterns of the M modulation signal. Further, by using the reference value based on the average number of times of reversal, it is possible to make the disk very hard to be affected by scratches, dirt, and the like. Also, EF
In practice, a circuit for measuring the number of inversions of the M signal can be simply configured with only a frequency divider.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A reproducing apparatus according to an embodiment of the present invention, in particular, a rotary servo circuit thereof will be described below with reference to FIGS. FIG. 1 shows a CLV of the reproducing apparatus according to the embodiment.
FIG. 3 is a block diagram of a rotary servo circuit included in a servo system and a CLV servo system. Reference numeral 1 denotes a disk, 2 denotes a spindle motor, and 3 denotes an optical head for reading data from the disk 1. Data read by the optical head 3 is output as an EFM signal via the RF amplifier 4.

As a CLV servo system, the EFM signal is PL
It is supplied to the L servo circuit 10 and the rough servo circuit 20. The PLL servo circuit 10 is configured to inject an EFM signal into the PLL circuit to reproduce a clock, compare the clock with a reference clock obtained by a crystal, and obtain rotation error information (rotation servo signal E _CLV-P ). ing. Then, the rotation servo signal E _CLV-P is supplied to the P terminal of the switching circuit 5.

The rough servo circuit 20 detects an average inversion value for the EFM signal, and compares the average inversion value with a target inversion value which is an average inversion value in the EFM signal extracted at a normal rotation speed. , _{So as} to obtain rotation error information (rotation servo signal E _CLV-S ). The rotation servo signal E _CLV-S is supplied to the S terminal of the switching circuit 5.

When the spindle motor 2 is started, the S terminal is selected in the switching circuit 5, so that the rotation servo signal E
_CLV-S is supplied to the motor driver 6. Then, the motor driver 6 supplies drive power to the spindle motor 2 according to the rotation servo signal E _CLV-S . In the meantime, PLL
In the servo circuit 10, the PLL circuit is locked.
A lock detection signal Lock is output according to the lock of the L circuit, and supplied to the switching circuit 5. When the lock detection signal Lock is supplied, the switching circuit 5 connects the P terminal, and thereafter supplies the rotation servo signal E _CLV-P to the motor driver 6 so that the CLV servo by the operation of the PLL servo circuit 55 is executed. I am trying to.

In the PLL servo circuit 10, first, an edge detection circuit 11 is provided to detect an edge of an EFM signal. The output of the edge detection circuit 11 is output from a phase comparator 12, a low-pass filter 13, a voltage-controlled oscillator (VC
O) is injected into the PLL circuit consisting of 14; That is, in this PLL circuit, the channel clock component is reproduced from the output of the edge detection circuit 11. VCO14
The output of the channel clock is 1 / N
The frequency is divided and input to the phase / frequency comparator 18.

Reference numeral 16 denotes a crystal reference clock generator. The reference clock from the reference clock generator 16 is divided by a frequency divider 17 into 1 / N and input to a phase / frequency comparator 18. When the PLL circuit of the phase comparator 12, the low-pass filter 13, and the VCO 14 is in a locked state, rotation error information is obtained by comparing the channel clock with the reference clock in the phase / frequency comparator 18. The output of the phase / frequency comparator 18 is phase-compensated by the phase compensating circuit 19 and supplied to the P terminal of the switching circuit 5 as a rotation servo signal E _CLV-P .

When the PLL circuit locks, a lock detection signal Lock is output from the phase / frequency comparator 18 to the switching circuit 5, whereby the switching circuit 5
Since the terminals are connected, the rotation servo signal E _CLV-P is supplied to the motor driver 6, and the CLV servo by the operation of the PLL servo circuit 55 is executed.

On the other hand, the PLL circuit is thus locked,
Until the PLL servo circuit 55 functions, the rough servo circuit 20 functions and the CLV servo is applied. That is, the rotation of the spindle motor 2 is controlled by the rough servo circuit 20 so that the EFM signal can be drawn into the capture range of the PLL circuit.

The rough servo circuit 20 includes a frequency divider 21, a frequency / voltage converter (F / V converter) 22, a target voltage generator 23, and a comparator 24. The operation of the rough servo circuit 20 will be described below.

First, FIG. 3, FIG. 4, FIG. 5, and FIG.
EF corresponding to each of the original 8-bit data up to F
M-encoded 256 EFM words (14
Bit). That is, it is an EFM conversion table. This EFM word is a pulse inversion signal of the so-called NRZi system. Therefore, the position of "1" is a pulse inversion position for each EFM word. Each figure has EFM
The word and the number of pulse inversions of the EFM word (that is, the number of “1”) are described.

[0029] The EFM word, from the 2 ¹⁴ possible patterns at 14 bits, which has been selected 256 ways to accommodate the 8-bit data, particularly during the "1" and "1", " The condition that two or more “0” s are satisfied is satisfied, and the inversion interval (interval between “1” and “1”)
The minimum inversion interval is 3T and the maximum inversion interval is 11T.

Here, the total number of inversions in one word shown for each EFM word in FIGS. 3, 4, 5 and 6 is as follows. EFM word with one inversion: 4 words EFM word with two inversions: 56 words EFM word with three inversions: 120 words EFM word with four inversions: 70 words EFM word with five inversions: 6 words

From this, the average number of inversions within one word is (4 × 1 + 56 × 2 + 120 × 3 + 70 × 4 + 6 × 5)
/ 256 = 786/256, which is almost three times less.

As described with reference to FIG. 7, the EFM frame has a sync pattern of 11T + 11T + 2T (that is, three inversions) and a margin bit of 3 bits arranged between each 14-bit EFM word. Therefore,
If the data to be EFM-encoded is a random number and the inversion occurrence probability at each margin bit is １ ／, the average number of inversions in one EFM frame is (786/256) × 33 + (１ ／) × 34 + 3 ≒ 1
21.32 [times]. Note that “33” is the number of words as main data, parity, and subcode, “34” is the number of margin bits, and “3” is the number of inversions of the sync pattern. (See Fig. 7)

For this reason, the average frequency of the EFM signal is (121.32 × 7.35 [KHz]) / 2 = 445.
85 [KHz]. The average frequency of this EFM signal is the same as the EFM signal from a mini-disc system or CD-ROM.
A system in which PCM audio data to be modulated is scrambled with M-sequence data, that is, EFM
In a system in which the data to be encoded is a random number, the value is almost reliable. Further, in a normal CD (CD digital audio), PCM audio data subjected to EFM modulation is not a perfect random number, so that the average frequency of the EFM signal may be somewhat unreliable. Value.

When the frequency of the EFM signal having such an average frequency is divided into, for example, 1/4096, (445.85 × 10 ³ ) /4096=108.85.
[Hz], an output frequency of 108.85 Hz is expected to be obtained.

That is, in the frequency divider 21 which performs 1 / n frequency division in the rough servo circuit 20 in FIG.
096, the output of the frequency divider 21 is 108.
It is expected that an output frequency of 85 Hz will be obtained.

The output frequency of the frequency divider 21 is converted into a voltage value by an F / V converter 22 and supplied to a comparator 24. Then, the target voltage value is supplied from the target voltage generator 23 to the comparator 24. The target voltage value is a voltage value corresponding to a frequency of 108.85 Hz.

Accordingly, the comparator 24 includes the F / V converter 22
And a voltage value corresponding to the average frequency of the EFM signal extracted from the disk 1 and the EF from the target voltage generator 23.
The comparison operation with respect to the target voltage value corresponding to the original average frequency of the M signal is performed.
The output of 4 becomes rotation error information. This is supplied to the S terminal of the switching circuit 5 as the rotation servo signal E _CLV-S ,
By being supplied to the motor driver 6, rough servo control of the spindle motor 2 is performed.

As described above, the rough servo circuit 20 of this embodiment
Is a frequency divider 21, an F / V converter 22, a target voltage generator 2
3. A very simple circuit configuration including only the comparator 24 is realized, and a remarkable downsizing is realized as compared with the conventional rough servo circuit. In addition, since the average frequency of the EFM signal is detected, the system is less affected by illegal signal patterns due to scratches and dirt on the disk, and a highly reliable system can be realized. Note that the frequency divider 21
Is not limited to 4096, and a suitable value may be set. That is, the frequency division ratio n may be set to a value at which the frequency division output is stable enough to fall within the capture range of the PLL system.

FIG. 2 shows another embodiment of the rough servo circuit 20. In this case, the rough servo circuit 20 includes a frequency divider 21, a target frequency generator 25, and a phase / frequency comparator 26. In this example, the average frequency obtained from the EFM signal by the frequency divider 21 is supplied directly to the phase / frequency comparison unit 26 without being converted into a voltage value.
As the target value, the target frequency (108.85 Hz) is supplied from the target frequency generator 25 to the phase / frequency comparator 26.

The phase / frequency comparison section 26 performs a comparison process on these inputs at the frequency level, and outputs error information, that is, the rotation servo signal E _CLV-S . Even with such a configuration, the same effect can be obtained.

Although the embodiment has been described with respect to the EFM signal, even if the modulation method is other than this,
The present invention can be applied to any device that records data using a run-length limited code.

[0042]

As described above, according to the present invention, the number of inversions of the EFM signal extracted from the disk is measured, and this is compared with a reference value to obtain rotation error information for rough servo. Therefore, there is an effect that a rotary rough servo circuit can be realized with an extremely simple circuit configuration. Further, by reducing the size of the rotary servo circuit, effects such as cost reduction and power consumption reduction can be obtained.

The reference value is predetermined based on the average number of inversions of all the generated patterns of the EFM signal. The rotation error information obtained thereby is less susceptible to illegal signal patterns due to scratches and dirt on the disk, and has the effect of realizing a highly reliable system, thereby obtaining the advantage of improving the performance of the system. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram of a reproducing apparatus and a rotary servo circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a rotary servo circuit according to another embodiment.

FIG. 3 is an explanatory diagram of an EFM word.

FIG. 4 is an explanatory diagram of an EFM word.

FIG. 5 is an explanatory diagram of an EFM word.

FIG. 6 is an explanatory diagram of an EFM word.

FIG. 7 is an explanatory diagram of an EFM frame.

FIG. 8 is a block diagram of a conventional rotary servo circuit.

[Explanation of symbols]

1 disk, 2 spindle motor, 3 optical head, 4 RF amplifier, 5 switching circuit, 6 motor driver, 10 PLL servo circuit, 20 rough servo circuit,
21 frequency divider, 22 F / V converter, 23 target voltage generator, 24 comparator, 25 target frequency generator, 26
Phase / frequency comparison unit

Claims (1)

[Claims] 1. A rotating means for rotating a disk-shaped recording medium, a reproducing means for reproducing a modulation signal recorded in the disk-shaped recording medium and modulated by an EFM method, and the modulation means reproduced by the reproducing means. Means for counting the number of times of inversion of the signal; means for comparing the number of times of inversion measured by the means for number of inversions with a reference value; and before the PLL is locked based on the comparison result of the means for comparison. Control means for controlling the rough servo rotation of the modulation signal, wherein the reference value compared by the comparison means is predetermined based on the average number of inversions of all the generation patterns of the modulation signal. Playback device.