JPH03290830A - Detecting method for eccentric quantity and eccentric direction in attaching disk medium - Google Patents

Abstract

PURPOSE:To execute the detection with high accuracy by applying an offset which increases stepwise by an isominute track pitch to an output of a position sensor of a track actuator, and executing the calculation by using a specific expression from an average value of the number of zero crossing points on a position error signal. CONSTITUTION:An offset is applied which increases stepwise by an isominute track pitch DELTATp to an output of a position sensor 19 of a track actuator 18 extending from '0' to a 1/2 or -1/2 track pitch, and whenever the offset increases by one step, the number N of zero crossing points on a position error signal corresponding to one rotation period is counted successively, and from its average value Nmean, the eccentric quantity at the time of attaching a disk medium is derived by using an expression, that is the eccentric quantity = (Nmean -2) * 0.5 Tp/4. In such a way, the eccentric quantity of the disk medium 1 can be detected easily and with high accuracy by a simple circuit constitution without being influenced by a spike noise, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for detecting the amount and direction of eccentricity when a disk medium is attached.

(Prior art) Reducing the cost per bit is an important issue in file storage devices that store large amounts of information, and it is necessary to position the data head on the track with high precision and achieve high areal recording density. be.

In order to position the head with high precision, it is important to widen the band of the servo system and improve the tracking performance of the servo system, but the same effect can be obtained by reducing the vibration of the data track, which is the reference for positioning. It will be done.

In an optical disk device, highly accurate tracks are formed on an optical disk medium using printing technology, so track runout is generally determined by eccentricity when the disk medium is attached. Therefore, the deviation between the center of rotation of a spiral or concentric track written on an optical disk medium and the center of rotation of the spindle motor that supports the optical disk medium and rotates it at high speed, that is, the amount of eccentricity and the direction of eccentricity, can be accurately detected. However, if this can be corrected, it becomes possible to achieve even higher track density.

The amount of eccentricity and the direction of eccentricity when a disk medium is attached in an optical disk device can be approximately measured from a position error signal, that is, a track runout signal, obtained when the optical head is locked with respect to the base. In addition, the position error signal has one period equal to 1
Since it is a sinusoidal signal corresponding to the track pitch,
Counting the number of zero-crossing points of the position error signal to obtain the wave number of the position error signal is the basis for detecting the amount of eccentricity and the direction of eccentricity. For this reason, in the past, the position error signal was differentiated to correspond to the zero-crossing point, as described in ``Measurement of eccentricity of optical disks'' (Proceedings of the 1985 National Conference of the Institute of Electronics and Communication Engineers, Lecture No. 1028). Generate pulses and find their number.

(Problem to be Solved by the Invention) However, the position error signal usually includes spike-like noise leaking from sector address information, switching noise from the spindle motor, etc., and this is not counted as the above-mentioned zero cross point. Therefore, in the conventional method, it is difficult to accurately detect the amount of eccentricity and the direction of eccentricity.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a method that can always accurately detect the amount of eccentricity and the direction of eccentricity regardless of spike noise, switching noise, etc.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a track actuator based on the output of a position sensor of the track actuator mechanically or electrically fixed to the base as a reference. In a method for detecting the amount of eccentricity when installing a disk medium in an optical disk device, in which a position M error signal 5) corresponding to the amount of eccentricity of the disk medium attached to the spindle motor is obtained when the spindle motor is fixed in the facing direction. O to 17 to the output of the actuator position sensor
Adding an offset that increases stepwise with an equally small track pitch ΔTp up to 2 track pitch (Tp) or -1/2 track pitch, and the zero crossing on the position error signal corresponding to one rotation period for each step increase in the offset. The number of points N (an integer of Nl2) is counted sequentially, the average value Nff1Oan is calculated, and the average value Nme
A method for detecting the amount of eccentricity when installing a disk medium, in which the amount of eccentricity when installing a disk medium is determined from an by using the following formula, amount of eccentricity = (Nmean-2) *0. 57p
/4 Also, as claimed in claim (2), when the track actuator is electrically fixed to the base based on the output of the position sensor of the track actuator mechanically or electrically fixed to the base, the spindle motor In a method for detecting eccentricity direction when a disk medium is attached to an optical disk device in which a position error signal corresponding to the eccentricity direction of the attached disk medium is obtained, an index detected by adding a first offset to the output of a position sensor of a track actuator is used. The time interval T0(n) between the zero crossing point on the position error signal and the output of the position sensor is
The time interval Tt(n) between the inch cross detected by adding the offset and the zero cross point on the position error signal
Change with ΔT(n) (=To(n)Tl(n))
are successively determined, two adjacent zero-crossing points M and M+1 (an integer of M≧1) on the position error signal where the sign of the change in time interval ΔT (n) changes are detected, and an index for the two zero-crossing points is detected. The time interval from TM.

We propose a method for detecting the eccentric direction when a disk medium is attached, which calculates the eccentric direction based on the index from TM+ using the following formula.

Eccentric direction = (TM +TM+1)π/TR or (T
M + TM + 1 ) π/TR + π (a!shi, TR is one rotation period) (Function) According to claim (1) of the present invention, when an offset is added to the output of the position sensor of the track actuator, the amount of eccentricity of the disk changes. When the corresponding position error signal changes and a predetermined offset amount is added, the number N of zero crossing points changes. The resolution of eccentricity according to the number of zero crossing points is 1/
Since the pitch is 2 tracks, the offset is O~1/
The average value when changing between 2 track pitches or 1172 track pitches is the number of zero cross points that are not affected by noise, and a more accurate eccentricity amount can be determined.

Furthermore, according to claim (2) of the present invention, when an offset is added to the output of the position sensor of the track actuator, the position on the time axis of the zero cross point on the position error signal corresponding to the eccentricity of the disk changes. , its change differs depending on the eccentric direction, and the zero crossing points located on both sides of the point where the eccentricity shows the maximum positive or negative value change in different directions. Therefore, the two zero-crossing points located on both sides of the eccentric direction are determined from the sign of the change in the time interval between two adjacent zero-crossing points from the index, and the eccentric direction is determined from the time interval between them.

(Example) FIG. 1 shows an overview of the position control system of an optical disk device that implements the method of the present invention. In the figure, 1 indicates an optical disk medium;
2 is a spindle motor, 3 is an optical head, 4 is a base,
5 is a positioner, 6 is a data signal reproduction system circuit, 7 is a position error signal reproduction circuit, 8 is a track actuator control circuit, 9 is a positioner control circuit, 10 is a position error signal reproduction circuit, 11 is a tracking and seek control circuit, 12゜13 is a driver. The optical head 3 also has a laser diode 15, a photodetector 16J, an optical system 17, a track actuator 18, and its position sensor 19 built into its housing 14, and also has a position sensor between it and the base 4 outside the housing 14. It is equipped with 20.

The positioner 5 roughly positions the optical head 3 based on a position error signal obtained from a position sensor 20 and a position scale (not shown) attached to the base 4. The beam emitted from the laser diode 15 is precisely positioned on the data track based on the position error signal reproduced via the photodetector 16 and the data signal reproduction system circuit 6. In this way, the beam is controlled in the optical disc loading system through two-step control using the positioner 5 and the track actuator 18, thereby achieving highly accurate positioning of 1/10 micron or less.

Further, the track actuator 18 has a dedicated position sensor 19, and if the positioning of the optical head 3 is controlled based on the output of this position sensor 19, the optical head 3 becomes locked with respect to the base 4. .

FIG. 2 shows the relationship between the trajectory 21 of the optical head on the optical disc medium 1 in such a locked state and the position 22 of the eccentric track on the optical disc medium 1.
Further, FIG. 3 shows a sinusoidal position error signal 23 reproduced from the previous disk medium 1 at this time. Note that here, point A and point B are the points where the eccentricity reaches the maximum positive value and the maximum negative value.

FIG. 4 shows a zero cross point 24 on the position error signal 23 corresponding to one rotation period (assuming, however, that the amount of eccentricity is sufficiently small with respect to the radius of the innermost circumference of the previous disk medium).

The position error signal is 1 for 1 track pitch (Tp).
It is a periodic sinusoidal signal, and the distance between zero crossing points on the position error signal corresponds to 0.5 track pitch. Therefore, by counting the number of zero-crossing points on the position error signal as shown in Fig. 4 over one rotation period, the amount of eccentricity can be calculated from the number of zero-crossing points at this time, for example N, with a resolution of 0.5 track pitch. It can be calculated as shown in equation (1).

Amount of eccentricity = (N-2) * 0.5Tp/4 (
1) (However, N is an even number) Here, if a positive offset is added to the track actuator control circuit 8, the radius of the trajectory of the optical head 3 will increase, so the displacement at point A will increase as shown in FIG. small,
The trajectory 25 has a large displacement at point B. Along with this, the position error signal changes as shown by the dotted line 26 in FIG. 6, and the zero cross point on the position error signal moves toward point A. Also, if you add a negative offset,
Since the radius of the trajectory of the optical head 3 becomes smaller, a trajectory 27 is formed in which the displacement at point A is large and the displacement at point B is small, as shown in FIG. Along with this, the position error signal changes as indicated by the dotted line 28 in FIG. 7, and the zero cross point on the position error signal moves toward point B.

Then, from the relationship between the position of the zero-crossing point on the position error signal with no offset and the amount of offset applied to the track actuator control circuit 8, the zero-crossing point on the position error signal may disappear at point A or point B. , new occurrences may occur.

FIG. 8 shows how the number of zero cross points changes as the offset amount changes. Here, for ease of explanation, it is assumed that the first zero-crossing point X1 on the position error signal 29 is located at point B with no offset.

Assume that positive and negative offsets are applied from the above state to move the fourth zero cross point x4 on the position error signal over 172 track pitches from x4' to the state of x4'' where it disappears at point A.In this case, the positive When the fourth zero-crossing point is located in the section from X4 to x4° due to the offset, the first zero-crossing point x1 is separated from point B and separated into two, so the number N of zero-crossing points on the position error signal 29 is 8. On the other hand, if the fourth zero-crossing point is located in the section from x4 to x4' due to a negative offset, the first zero-crossing point x1 disappears at point B, so the number of zero-crossing points in the position error signal 29 is 6. become individual.

Then, the proportion of the area where N=8 is the offset amount until the fourth zero cross point x4 disappears at point A,
In other words, the distance between points A and B, which corresponds to twice the amount of eccentricity, is 1.
It is proportional to the remainder when counted with a resolution of 72 track pitches.

As a result, an offset is added to the output of the position sensor 19 that increases stepwise from 0 to 1/2 track pitch or 1 1/2 track pitch at an equal minute track pitch ΔTp, and each one step increase in the offset results in one rotation period. The number of zero crossing points N on the position error signal corresponding to
(N≧1 integer) is counted sequentially, and its average value N me
If an is determined, the amount of eccentricity when the optical disk medium is attached can be calculated as shown in equation (2).

Eccentricity ff1= (Nmean-2) *0.5Tp/
4...(2) In the present invention, the radius of the trajectory of the optical head on the optical disk medium is changed by offset, and the number of zero crossing points on the position error signal corresponding to one rotation period is counted,
Since the amount of eccentricity is calculated from the average value, even if a signal that is recognized as a zero cross point is generated due to spike noise caused by media noise or media defects, the effect on the counting results is slight, and the eccentricity can be calculated with high accuracy. It has the characteristic of being able to measure quantities.

FIG. 9 shows an embodiment of a position error signal reproducing circuit that implements the eccentricity detection method of the present invention. In the figure, 31 is a zero-crossing detection circuit for the position error signal, 32 is a zero-crossing pulse counter, and 33 is calculating the average value Nmean of the number N of zero-crossing points per rotation period while adjusting the offset according to the flow of the program shown in FIG. A microprocessor, 34 a switch for changing the control state of the track actuator, and 35 a D for providing an offset signal.
/A converter 36 is an analog adder. In this configuration, the amount of eccentricity when the disk medium is attached is detected according to the following procedure.

First, in order to lock the track actuator 18,
The switch 34 is switched to the position sensor 19 output side. In this state, a sinusoidal position error signal corresponding to eccentricity can be obtained from the optical head 3, and a zero cross pulse corresponding to a zero cross point on the position error signal is generated by the zero cross detection circuit 31. The zero-crossing pulse counter 32 counts the number of zero-crossing pulses between index pulses, that is, the number of zero-crossing points, and transfers the count to the microprocessor 33.

Next, the microprocessor 33 sends the offset data of the track actuator 18 via the data bus 37 to D.
/A converter 35 and added to the track actuator control circuit 8 as an analog quantity. In this offset state, the number of zero-crossing points is counted in the same manner as described above and is taken into the microprocessor 33.

The microprocessor 33 changes the offset amount from O to 1/
While gradually changing the track pitch ΔTp to 2 track pitch or 1 1/2 track pitch,
Count the number of zero cross points and calculate the average value Nff1c
an is determined, and the amount of eccentricity is calculated according to formula <2>.

On the other hand, as is clear from FIGS. 5, 6, and 7,
On the right half circumference and the left half circumference of the diameter passing through points A and B of the optical disk medium, the direction of movement of the zero cross point on the position error signal when an offset is added is opposite. Therefore, if we find two adjacent zero-crossing points that move in different directions when an offset is added, the midpoint between them will be point A or point B, and the time interval between the index and the two zero-crossing points will be TM, TM+1. Then, the eccentric direction can be calculated using equation (3) with the index as a reference.

Eccentric direction = (TM +TM+1)π/TR or (T
M + TM + 1 ) π / T R + π (3
) (However, TR is one rotation period) Furthermore, when specifying the direction of eccentricity in equation (3), the position error is All you have to do is check the direction in which the zero-crossing point on the signal moves. For example, in the case of Figures 6 and 7, when a positive offset is added, the time interval between the index and the zero-crossing point on the position error signal increases. There is a point A in the direction, that is, a positive eccentric direction.

FIG. 11 shows an embodiment of a position error signal reproducing circuit that implements the eccentric direction detection method of the present invention. In the figure, 41 is a zero-crossing detection circuit for position error signals, 42 is a zero-crossing pulse counter, 43 is an event timer that measures the time interval T (n) between the index and the nth zero-crossing pulse, and 44 is the program shown in FIG. A microprocessor stores the time interval T (n) according to the flow of the process and calculates the change ΔT (n) in the time interval T (n) depending on the presence or absence of an offset, 45 is a switch for switching the control state of the track actuator 18, and 46 is an offset A D/A converter 47 that provides a signal is an analog adder. In this configuration, the eccentric direction of the disk medium is detected according to the following procedure.

First, in order to lock the track actuator 18,
Switch 45 is switched to the position sensor 19 output side. In this state, a sinusoidal position error signal corresponding to eccentricity can be obtained from the optical head 3, and a zero cross pulse corresponding to a zero cross point on the position error signal is generated by the zero cross detection circuit 41. On the other hand, the zero-crossing pulse counter 42 receives a desired zero-crossing point number n via the address bus 48 of the microprocessor 44.
is input as a preset value, the number of zero-crossing pulses after the index pulse is manually input is counted, and an event pulse is generated when the count value matches the preset value, that is, the desired zero-crossing point number n. The time interval T0(n) between this event pulse and the index pulse is measured by the event timer 43,
stored in memory within microprocessor 44;

Next, the microprocessor 44 inputs the offset data of the track actuator 18 via the data bus 49.
/A converter 46 and added to the track actuator control circuit 8 as an analog quantity. In this offset state, the time interval T1(n) is measured in the same manner as described above and is stored in the memory of the microprocessor 44. Note that the amount of offset in this case is preferably 174 track pitches or less, which is half the interval between the zero cross points on the position error signal, because it is necessary to identify the movement of the zero cross points.

After this, the microprocessor 44 changes the time interval ΔT(n) (=To (n) T+ (n)
) are sequentially calculated, two adjacent zero-crossing points M and M+1 on the position error signal where the sign of the time interval change ΔT (n) changes are determined, and the time intervals TM, TM from the index for the two zero-crossing points are calculated.
, , the eccentric direction with respect to the index is calculated as the delay time from the index.

In addition, in this embodiment, if point A or point B, where the eccentricity is maximum, sways around the zero cross point of the position error signal due to disturbance etc., the position where the sign of the change in time interval ΔT (n) changes. It becomes difficult to identify two adjacent zero crossing points M and M+1 on the error signal. In such a case, the time interval T (n
), it is sufficient to shift the reference measurement point by giving another offset in advance. In addition, point A and point B are detected independently under optimal offset conditions, and the time interval TA from index to point A and the time interval TA from index to point B are detected.
If the time interval TB up to the point is determined individually and averaged as shown in equation (4) to detect the eccentric direction, more accurate detection becomes possible.

Eccentric direction = (TA 10 (TR/2 7B))
/2...(4) (Effects of the Invention) As pointed out above, according to claim (1) of the present invention, an offset that increases in a stepwise manner is given to the optical head to improve the position error signal. Since the amount of eccentricity is calculated by calculating the number of zero-crossing points on the position error signal corresponding to one rotation period while moving the iri range of the zero-crossing point by equal minute track pitches, it may be affected by spike noise, etc. Therefore, the amount of eccentricity of the disk medium can be easily and accurately detected with a simple circuit configuration.

Further, according to claim (2) of the present invention, an offset is given to the optical head to move the position of the zero cross point on the position error signal, two zero cross points having different moving directions are found, and the eccentric direction is calculated. As a result, the eccentric direction of the disk medium can be easily and accurately detected with a simple circuit configuration without being affected by spike noise or the like.

Furthermore, according to the present invention, compared to the conventional method of differentiating a position error signal to detect a zero-crossing point, the present invention measures the position of a zero-crossing point on the time axis, so it is suitable for signal processing by a microprocessor. Therefore, it is easy to apply to digital control circuits that are essential for downsizing optical disk devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an overview of the position control system of an optical disk device that implements the method of the present invention, FIG. 2 is an explanatory diagram showing the relationship between the trajectory of the optical head and the position of an eccentric track, and FIG. 3 is a position diagram showing the position of an eccentric track. A waveform diagram showing an example of the error signal, FIG. 4 is an explanatory diagram showing the arrangement of zero cross points on the position error signal, and FIG.
The figure is another explanatory diagram showing the relationship between the trajectory of the optical head and the position of the eccentric track. Figure 6 is a waveform diagram showing the position error signal when offset to the positive side. Figure 7 is a waveform diagram showing the position error signal when offset to the negative side. FIG. 8 is an explanatory diagram showing how the number of zero cross points changes on the position error signal. FIG. 9 is a position error signal reproducing circuit that implements the eccentricity detection method of the present invention. FIG. 10 is a flowchart of a program for detecting the amount of eccentricity, and FIG. 11 is a configuration diagram showing an embodiment of a position error signal reproducing circuit that implements the eccentricity direction detection method of the present invention. , FIG. 12 is a flowchart of a program for eccentric direction detection. 1... Optical disk medium, 2... Spindle motor,
3... Optical head, 4... Base, 7... Position error signal reproducing circuit, 8... Track actuator control circuit, 18... Track actuator, 19...
Position sensor, 31.41...Zero cross detection circuit, 3
2゜42...Zero cross pulse counter, 33.44
...Microprocessor, 34.45...Switch, 35.46...D/A converter, 36.47...Adder, 43...Event timer.

Claims (2)

[Claims] (1) When the track actuator is electrically fixed to the base based on the output of the position sensor of the track actuator mechanically or electrically fixed to the base, the amount of eccentricity of the disk medium attached to the spindle motor In a method for detecting the amount of eccentricity when installing a disk medium in an optical disk device in which a corresponding position error signal is obtained, the output of the position sensor of the track actuator is set from 0 to 1.
/2 track pitch (Tp) or -1/2 track pitch, an offset that increases stepwise with an equal minute track pitch ΔTp is added, and each step increase in the offset increases the position error signal corresponding to one rotation period. Number of zero cross points N (N≧1
(an integer number) is sequentially counted, the average value Nmcan is determined, and the eccentricity when installing the disk medium is calculated from the average value Nmcan using the following formula. Detection method. Eccentricity = (Nmcan-2)*0.5Tp/4 (2) When the track actuator is electrically fixed to the base based on the output of the position sensor of the track actuator mechanically or electrically fixed to the base, the eccentric direction of the disk medium attached to the spindle motor In the eccentric direction detection method when installing a disk medium in an optical disk device, which obtains a corresponding position error signal, the index detected by adding the first offset to the output of the position sensor of the track actuator and the zero cross point on the position error signal are Time interval T_0(n),
Change ΔT(n) (=T
_0(n)-T_1(n)) are successively determined, and two adjacent zero-crossing points M and M+ on the position error signal where the sign of the change ΔT(n) in the time interval changes.
1 (an integer of M≧1), and the time intervals T_M, T_ from the index for the two zero crossing points are detected.
A method for detecting an eccentric direction when installing a disk medium, characterized in that the eccentric direction with reference to an index is calculated from M_+_1 using the following formula. Eccentric direction = (T_M+T_M_+_1)π/T_R or (T_M+T_M_+_1)π/T_R+π (However, T
_R is one rotation period)