JPH0449524A - Defect detecting circuit for sample servo pit - Google Patents

Abstract

PURPOSE:To use defect information and to quickly work out a countermeasure against a defect by directly calculating sample pit information outputted for each segment to detect the defect or the abnormality of pits by a defect detecting circuit. CONSTITUTION:Detection signals of a clock pit and a wobbling pit arranged in each segment are detected by sampling circuits 11B, 11A, and 11C and are supplied to coefficient devices 12A to 12B and are controlled to a prescribed level. A first signal E1 is generated with respect to vector by subtraction between detection signals Sc and Sw2 in a subtractor 13A, and a second signal E2 is generated by addition between detection signals Sc and Sw1 in a subtractor 13B. Outputs of subtractors 13A and 13B are supplied to square circuits 14A and 14B and are added by an adder 15 again. An output E of the adder 15 and a reference value F of a reference level signal 17 are compared with each other by a comparator 16, and the signal of the difference is inputted to an absolute value circuit 18, and a defect detector 19 is operated when the output value exceeds a certain value or larger.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is directed to a sample servo pit detection method that can detect defects in sample servo pits that have been formed in advance to form recording tracks of magneto-optical disks. It is related to circuits.

[Summary of the Invention] A sample servo pit detection circuit in a magneto-optical disk of the present invention detects a pair of wobbling pits arranged concentrically at a predetermined interval to form a recording track, and In order to effectively detect defects in the clock pits that form the clock reference of This allows defects in sample servo pits to be detected immediately.

3. Detailed Description of the Invention [Prior Art] A magneto-optical disk capable of recording data in response to light has concentric recording tracks or spiral recording tracks in the shape of a pre-group in advance. There are those that are stamped and those that form recording tracks using sample servo pits that are discretely arranged.

FIG. 5 shows the format of a magneto-optical disk in which recording tracks are formed by sample servo pits, and S, -S, and □ represent sectors divided into 32 in the circumferential direction, for example.

Each sector S track has an address area AD and a following 18-byte data area for 42 segments S.
The data is divided into 42 parts and recorded.

In each segment SG, for example, as shown in FIG. 6, 2-byte servo bytes SB are arranged first, followed by 16-byte data bytes DB1 to DBn.

The servo tool SB is embossed in advance with a pair of wobbling pits P, P2 and a clock pit P3 arranged on the center line of the track T, which are offset toward the outer and inner circumferences with the track T as the center. It is formed by processing etc.

Warbling Pit P, P2 and Clock Pit P
3 is a mirror surface MR, and a focus servo signal is detected by the laser beam reflected from this mirror surface, and the laser power can be controlled.

In the case of such a magneto-optical disk, a tracking error signal can usually be generated by calculating the reflected light when the wobbling pits P, , P, are detected at the sample point tt2, and the tracking error signal can be generated by calculating the reflected light when the wobbling pits P, , P, are detected at the sample point tt2. A data read clock (channel clock) is formed by the signal detected at the sample point t3.

The channel clock is usually formed by a PLL circuit that determines the peak point from the reflected light from the clock pit and controls the voltage controlled oscillator using a signal that compares the timing signal at the peak point with the phase of the output of the voltage variable oscillator.

[Problem to be Solved by the Invention 1] Such a sample servo pit type magneto-optical disk, while sampling each sample pit point,
Clock information and tracking information can be obtained, but if a defect occurs in the sample servo pit during the manufacturing process of the magneto-optical disk, it will not only be impossible to construct a proper servo circuit, but especially if a large defect occurs in the clock pit, If the clock signal that serves as a reference for reading or writing data is fluctuated, serious accidents such as frequent occurrence of erroneous data or data being recorded at the wrong position occur.

Therefore, in the conventional case as well, P
It is known to monitor the output of the phase comparator of the L L circuit and detect abnormalities in the clock pit.
The detection method using the error signal of the LL circuit has the problem that accurate defect detection is not necessarily performed, and at the same time, there is a problem that there is a time delay in taking countermeasures in the case of a bit defect because there is a lag between the bit defect position and the detection timing. was there.

[Means for Solving the Problems 1] The present invention solves these problems and enables more clear defect detection by using a clock signal detected from a clock pit located on the track center line;
It is equipped with a subtraction means for subtracting two signals obtained from the wobbling pits that are deviated from the center of the track toward the inner and outer circumferences, and addition that squares the levels of the two subtracted signals. We have measures in place.

Then, when the added output deviates from a constant value, it is determined that the servo bit is defective.

[Function] Since the wobbling pit is located at a position offset from the clock pit located on the center line of the track, the detection signal of one wobbling pit is different from the detection signal of the clock pit. The first subtracted
and a second value obtained by subtracting the other wobbling pit from the clock pit will change with a phase difference of 90·.

Therefore, if each servo bit is normal, the first
The square of the value and the square of the second value are always a constant value (1), and it can be determined that there is no defect in the clock pit.

[Embodiment] FIG. 1 is a block diagram of an embodiment for detecting defects in sample servo pits according to the present invention, and l is a magneto-optical disk on which sample servo pits are formed as described above. , 2 is a motor that rotates the magneto-optical disk l, and 3 is an optical pickup that reads data from the magneto-optical disk, which can be in a recording mode for recording data on the magneto-optical disk.

Reference numeral 4 indicates an RF signal reproduction amplifier, and the reproduction output is supplied to the defect detection section 10 of the present invention via the A/D converter 5.

Further, the reproduction signal obtained from the sample servo pit and the data area is supplied to the servo control circuit 6 and the reproduction signal processing section 7.

The servo control circuit forms a tracking error signal and a focus error signal from the signal obtained from the sample servo pit, and supplies them to a servo circuit (not shown), and at the same time extracts a clock signal CLK and extracts data from the RF signal. I do.

Further, the sample pulse formed from the clock signal is sent to the sampling circuit 11A of the defocus detection section 10,
The signal is supplied to JIB and IIc, and the aforementioned wobbling pits and clock pits are detected.

The detection operation of the defect detection section 10 will be explained below.

The detection signals of clock pits and wobbling pits arranged in each segment are detected by the sample circuit 11.
B, IIA, and IIC, respectively, are detected by coefficient unit 1.
2A-12B and is controlled to a predetermined level.

As shown in Fig. 2, with respect to the clock pit Pe placed on the center line of the track T, the wobbling pits p, , p, □ are placed at points shifted from each other by the respective track distances, so the magneto-optical When the spot is shifted in the radial direction of the disk, the traverse signal of each bit outputted will be shifted by a phase difference of 90 degrees.

That is, as shown in FIG. 3, the detection signals S w++ Swi of the wobbling pits p w+ and P wz have a vector phase difference of ±90· with respect to the detection signal Sc of the clock pit PC.

Therefore, these signals change as shown by solid lines and dotted lines in FIG. 4 during traversal.

When the detection signals Sc and S 1112 are subtracted by the subtracter 13A, a first signal E is formed in a vector sense, and when the detection signal Sc and the detection signal S w+ are added in the subtracter 13B, a first signal E is formed in a vector sense. A second signal E2 is formed.

Since the first signal E1 and the second signal E2 change as shown in FIG. 4, for example, if the first signal E is expressed as A sinωL, the second signal E2 is expressed as A cosωt.

The outputs of the subtracters 13A and 13B are supplied to two east circuits 14A and 14B, respectively, and are added together again by an adder 5.

Therefore, the output E of the adder 15 is E=(A-sin ωt 12+(A・cos
ttrL)”A2・・・・・・・・・・・・・i
It becomes a constant value of ll.

Equation (1) above holds true when the phase difference between the first signal E1 and the second signal E2 is 90° in FIG. The pit PC detection signal Sc is essential.

That is, where there is a defect in a portion of the magneto-optical disk and the clock pit PC is missing or abnormal during reproduction or recording, the above formula C11 does not hold.

Therefore, the output E of the adder 15 and the reference level signal 17
The reference value F of is compared with the comparator 16, the signal of the difference is inputted to the absolute value circuit 18, and if the output value exceeds a certain value, the defect detector 19 is activated. At least, it becomes possible to immediately detect defects in the clock pit PC.

In addition, when the defect detector 19 detects a defect in the clock pit PC several times in succession, for example, the PL
Erroneous recording can be prevented by holding the control signal of the L servo circuit and temporarily interrupting the recording mode.

Such defects can be detected in each segment of the magneto-optical disk! Since the detection is performed at the second position, the defect detection speed is increased and countermeasures can be taken quickly.

Defect detection according to the present invention can be performed not only while writing information to a track, but also while seeking a desired track.

In addition, it has the advantage that it can be used to detect defects in wobbling pits as well as clock pits.

[Effects of the Invention] As explained above, the sample servo pit defect detection circuit of the present invention directly calculates the sample pit information output for each segment to detect bit defects and abnormalities. This method has the advantage that it is possible to quickly take measures against defects by using information about defects that occur during operation of the magneto-optical disk.

Furthermore, since defect detection can be performed even during a data seek operation, the quality control of the magneto-optical disk is improved and the occurrence of erroneous data can be prevented.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of a sample servo pit, Fig. 3 is a vector diagram showing the detection signal of the sample servo pit and its phase, and Fig. 4 is a calculated diagram. FIGS. 5 and 6 are explanatory diagrams of the recording format and sample servo pits of the magneto-optical disk. In the figure, IIA, IIB, and IIC are sampling circuits, 1
3A and 13B are subtracters, 14A and 14B are square circuits, 1
5A indicates an adder.゛gu′gu

Claims (1)

[Claims] Detecting means for detecting a pair of wobble pits that are respectively deviated from the center of the spirally formed track toward the inner circumference and the outer circumference, and a clock pit provided on the track center line; first and second subtracters that respectively subtract reproduction signals of the pair of detected wobbling pits and the clock pit; and a first subtractor that squares the outputs of the first and second subtracters, respectively. and a second multiplier, and a defect determination circuit that adds the outputs of the first and second multipliers and determines a defect in the sample pit from fluctuations in the addition power level. Servo pit defect detection circuit.