JPH05109179A - Eccentricity measuring method - Google Patents

Abstract

PURPOSE:To provide an easy eccentricity measuring method which does not require a large capacity memory. CONSTITUTION:In an eccentricity amount detection circuit 80, an amount of displacement (h) of an optical head 10 is measured and an amount of displacement (d) of a disk 11 is computed by d=(1+F1/H1).(1/F2).h where H1 is a transfer function of the optical head, Fl is a transfer function of a driving motor and F2 is a transfer function of a measurement filter. Then, based on the frequency of the amount of displacement (d), a maximum value Dmax of (d) is computed. Furthermore, a phase difference phi between the zero cross point of (d) and the reference position of an encoder 20 is computed and an amount of eccentricity D (theta) is computed by D (theta)=Dmax.sin (theta+phi).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eccentricity measuring method used in an optical recording / reproducing apparatus such as a CD player for correcting track deviation due to eccentricity of a recording medium when coarsely feeding an optical disk. Is.

[0002]

2. Description of the Related Art Conventionally, in a CD player or a CD-ROM player, in order to reach a normal target track, first,
The number of tracks from the track where the optical head is currently located to the target track is calculated, and the feed motor control unit determines the feed motor without counting the number of tracks traversed by the optical head at a given speed. It moves in time (this is called "coarse feed"). And
When the rough feed is completed, the time information on the position of the optical head is read.

Therefore, in order to realize high-speed access of a CD player or the like, it is necessary to bring the optical head as close to the target track as possible during rough feed.

By the way, when the optical disc is mounted on the spindle motor, the track axis of the optical disc and the spindle motor are affected by the accuracy of the center hole of the optical disc, the error when fixing the optical disc to the spindle motor, and the like. It is well known that it does not coincide with the axis of rotation of. When the spindle motor is rotated in this state, the optical beam is displaced by a predetermined distance from the center of the track. As a method for measuring the displacement (amount of eccentricity) between the optical beam and the track center, there is a method disclosed in Japanese Patent Application Laid-Open No. 61-967.

According to this method, first, an optical disk is placed on a turntable, the optical head is moved so as to read information from the innermost circumference of the optical disk, and the spindle motor is moved at a constant angular velocity. The focus control system is turned on to turn on the focus control system, and the track tracking control of the track tracking control system is turned off to detect track information and obtain a track signal. Then, from the rotation axis on the optical disc, a predetermined radius R
The frequency / voltage conversion is performed on the track signal obtained by making a round in the part of. If the voltage obtained at the position of an angle θ is V and the eccentricity per unit voltage is δ,
The eccentricity D (θ) at the position of the angle θ is D (θ) = V ·
It is calculated as δ.

[0006]

However, the conventional eccentricity measuring method described above has the following problems. In order to obtain the amount of eccentricity at an arbitrary angle, it is necessary to store a track signal for one round of the optical disc or a signal after frequency / voltage conversion, which requires a large capacity memory. Since the optical head is transferred to obtain the track signal and the frequency and voltage of the track signal are converted, the processing becomes complicated.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide an eccentricity measuring method which does not require a large capacity memory by a simple method.

[0008]

In order to solve the above problems, the present invention provides an encoder for detecting a reference position and an angle, an optical head control means for controlling an optical head, and a feed motor. An optical disc device having a feed motor control means for controlling the optical disc and performing track servo by using the optical head control means and the feed motor control means, wherein the eccentricity of the optical disc is at a desired angle θ. The eccentricity measurement method for obtaining the amount D (θ) is performed by measuring the displacement amount h of the optical head,
The displacement amount d of the optical disk is d = (1 + F1 / H1). (1 / F2) .h, where H1 is the transfer function of the optical head, F1 is the transfer function of the feed motor, and F2 is the transfer function of the measurement filter. Based on the frequency f of the displacement amount d, a second step of calculating the maximum value Dmax of the displacement amount d, and the phase and encoder of the displacement amount d at the zero cross point. The phase difference φ from the phase at the reference position is calculated, and the eccentricity amount D (θ) is calculated from D (θ) = Dmax · sin (θ + φ).

In the first step, the frequency f of the displacement amount d is measured, and the displacement amount d is calculated by using the correction coefficient based on the frequency f.

In the second step, the maximum value Dmax of the displacement amount d is calculated by obtaining the position where a quarter cycle has elapsed from the zero cross point of the displacement amount d.

In the third step, the eccentricity amount D (θ) is calculated by using the sine waveform stored in advance.

[0012]

The present invention comprises the eccentricity measuring method as described above,
Since the maximum displacement amount is calculated from the displacement amount of the optical head and the displacement period, and the eccentricity amount is calculated from the maximum displacement amount and the phase difference, the eccentricity amount can be accurately determined by a simple method.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an optical head controller to which the present invention is applied. In the figure, 10 is an optical head,
20 is an encoder, 30 is a reference position detection sensor, and 40
Is an angle detecting sensor, 50 is a CPU, 60 is an optical head controller, 70 is a feed motor controller, 80 is an eccentricity detection circuit, and 90 is a ROM. The optical head 10 is a guide bar.
Along the lines 15 and 15 ', a feed motor (not shown) moves the disc 11 from the outer peripheral side to the inner peripheral side or from the inner peripheral side to the outer peripheral side.

The encoder 20 is attached to a rotary shaft of a spindle motor (not shown), and as shown in FIG. 2, a reference position detecting marker 35 has one groove and an angle detecting marker 4 is provided.
5 is engraved with 100 grooves at 3.6 degree intervals. Further, the encoder 20 has a reference position detecting sensor 30 for detecting the reference position detecting marker 35 and an angle detecting sensor 40 for detecting the angle detecting marker 45.
Are installed, and each of them is a marker 3 for detecting the reference position.
5. If the marker 45 for angle detection is detected, PULSEZ, PULS
The EA signal is output to the CPU 50. PULSEA signal is C
It is used as an external clock of the angle detection counter 51 provided in the PU 50, and the PULSEZ signal is used as a reset signal of the angle detection counter 51.

Next, the measurement of the amount of eccentricity and the creation of the map of the amount of eccentricity according to the present invention will be described. It is known that the amount of eccentricity of a disk can be represented as an eccentricity map of a sine waveform except for complicated deformation. Particularly, in a 5-inch disc such as a CD or a CD-ROM, the disc has a small diameter, so that the disc has a high rigidity and the deformation of the secondary or higher is extremely small. Therefore, assuming that the amount of eccentricity is D (θ), D (θ) can be approximated by the equation (1). D (θ) = Dmax · sin (θ + φ) (1) Here, Dmax is the maximum value of the eccentric amount D (θ), and φ is the phase difference. Therefore, in the present invention, the above-mentioned Dmax and φ
Is measured and stored to calculate the eccentricity amount.

Next, the measurement of Dmax will be described.
The tracking that is usually performed is performed by the sum of the movement of the lens by the optical head 10 and the movement by a feed motor (not shown). Therefore, it is necessary to measure both the movement by the optical head 10 and the movement by the feed motor for the measurement of the eccentricity. By the way, when the track servo as shown in FIG. 3 is operating, the displacement fm of the feed motor is expressed as shown in the equation (2),
Therefore, the amount of eccentricity S is expressed by equation (3). fm = (h / H1) · F1 (2) S = (1 + F1 / H1) · h (3) where H1 is the transfer function of the optical head, F1 is the transfer function of the feed motor, and h is the transfer function of the optical head. Displacement.

Further, when measuring the displacement of the optical head, paying attention to the fact that the frequency of the eccentricity S is the same as the rotational speed of the disk 11, and by adding a measurement filter as shown in FIG. To reduce the measurement error caused by the above and improve the measurement accuracy. In such a case (3) above
The formula can be rewritten as: S = (1 + F1 / H1) * (1 / F2) * h (4) where F2 is the transfer function of the measurement filter. Further, the measurement filter may have a frequency characteristic that allows the rotating frequency of the disk 11 to pass.

Next, the specific flow of the present invention will be described with reference to FIGS.
And FIG. 5 will be described. When the disk 11 is loaded, the feed motor control unit 70 first operates a feed motor (not shown) to move the optical head 10 to the innermost peripheral side of the disk 11, and 00: The disk 11 is searched at the 02:00 position (step ST50).
1). The signal read by the optical head 10 in step ST501 is input to the eccentricity amount detection circuit 80.

The eccentricity detection circuit 80 detects a zero-cross point of the signal read from the disk 11 and falls at the point of turning from the minus side to the plus side and rises at the point of turning from the plus side to the minus side. D
SI is generated and output to the CPU 50. The read signal is output to the CPU 50 as the signal DS. The signal input to the eccentricity amount detection circuit 80 corresponds to d in FIG.

DS output to CPU 50, DS
I is as shown in FIG. In the CPU 50, the angle detection counter 51 stepped by PULSEA is reset at the fall of DSI. Since the angle detecting marker 45 is engraved in the encoder 20 by 100 grooves, the angle detecting counter 51 is reset every 100 counts by the fall of DSI. Since DS can be regarded as a sine wave, the maximum eccentricity is obtained when the counter value is 25, as shown in FIG. In this example,
D when the counter value is 25 to reduce the measurement error
The reference voltage value VR output from S and the reference voltage generation circuit 55 is measured four times and the average value thereof is taken (step ST502). Then, the difference between the calculated average value of DS and the calculated average value of VR is calculated to calculate the maximum eccentricity amount DS_AVR (step ST503). It should be noted that this DS_AVR has a loss of gain and needs to be corrected using an eccentricity circuit correction coefficient, which will be described later.

Next, the phase difference DIF_PH between DSI and PULSEZ
Ask for S. At this time, the counter of the CPU 50 is PULSEZ
Set to be reset by. Here, FIG. 8 is a diagram for explaining calculation of the phase difference DIF_PHS. As mentioned above, PULSEZ is once every time the encoder 20 makes one revolution,
The reference position detecting sensor 30 is a reference position detecting marker 35.
Is generated every time is detected. Therefore, as shown in the figure, the counter value becomes "0" when PULSEZ becomes "H", and when the counter value is read at the fall of DSI, the phase difference DIF_
PHS is obtained. The actual phase difference is (100-DIF_PH
S) (100 is a counter value obtained during one revolution of the encoder 20) is further corrected for the phase delay. Such correction is performed when coarse feed is performed (hereinafter, "rough feed").
That is).

Next, the specific flow of the present invention during rough feed will be described. FIG. 9 is a diagram showing a processing flow of eccentricity correction performed at the time of rough feed. In this process,
First, read the counter of the CPU 50 and read the current angle CUR_
Obtain PHS (step ST901). Then, the actual eccentric angle ADJ_PHS is obtained from the current time, the eccentric circuit correction coefficient, DIF_PHS and CUR_PHS (step ST902). In step ST902, the actual phase difference is (10
0-DIF_PHS) and that the positions of the optical head 10 and the reference position detection sensor 30 are deviated by 180 degrees with respect to the rotation axis of the encoder 20. In addition,
ADJ_PHS is represented as data in the first quadrant, and information indicating in which quadrant it is located is added. Also, ADJ_
PHS corresponds to (θ + φ) in equation (1).

The eccentricity circuit correction coefficient will be described below. FIG. 7 is a diagram showing the eccentricity circuit correction coefficient.
The eccentricity circuit correction coefficient is for correcting the loss of the gain (gain) and the delay of the phase generated in the measured amount of eccentricity, and as shown in the figure, the gain and the phase corresponding to the frequency are made into a table, Each is stored in the ROM 90. The CPU 50 measures the frequency of eccentricity, that is, the number of rotations of the disk 11, and outputs the address signal corresponding to the frequency as R.
Output to OM90 to obtain gain and phase. For example, if the frequency is 4.06Hz, the gain is 9
2%, and the phase is delayed by 200 degrees. Therefore, the CPU 50 executes the step ST in FIG.
A value obtained by correcting the value DS_AVR obtained in step 503 using the eccentricity correction circuit coefficient becomes the true maximum eccentricity amount, that is, Dmax in the equation (1).

Subsequently, ADJ_PHS, DS_AVR and ROM 90
Number of eccentricity error tracks from the sine waveform stored in
K_VL is obtained (step ST903). Hereinafter, the process in step ST903 will be described in detail. RO
The sine waveform data stored in M90 has data for 1/4 cycle of the sine waveform. Since 100 counts in the angle detection counter 51 of the CPU 50 correspond to one cycle of the sine waveform, the sine waveform of 1/4 cycle is divided into 25 and each angle is corresponded at an interval of 3.6 degrees. You just have to have the data to do.

Further, in this embodiment, the eccentricity amount when the value of DS is 1 V is 100 μm, the reference voltage VR input to the CPU 50 is 5 V, and the A / D conversion resolution of the CPU 50 is 256. When the track width of the disk 11 is 1.6 μm, the maximum amplitude D of the sine waveform is expressed by equation (5). D = (5 · 100) / (256 · 1.6) (5) Therefore, the data of the sine waveform for each angle is as shown in FIG. However, as it is, it is necessary to display the floating point number in order to maintain the accuracy, so in the present embodiment, this is multiplied by 200, and FIG.
The data as shown in (b) is stored in the ROM 90.

Therefore, the finally obtained eccentricity error track number TRACK_VL can be expressed as in equation (6). TRACK_VL = (1/200) * DS_AVR * sin (ADJ_PHS) (6) For example, when the calculated DS_AVR is 36 (H), that is, 54 (DEC), the number of eccentricity error tracks TRACK_VL at each angle is It is obtained as shown in FIG.

Further, the gain of the eccentricity error track number TRACK_VL is corrected by the current time on the disk 11 and the eccentricity circuit correction coefficient to obtain the true error track number REL_VAL (step ST904).

The CPU 50 determines the number of error tracks obtained.
Based on REL_VAL, the time for moving the feed motor is corrected and an instruction is given to the feed motor control unit 70.
Then, the feed motor control unit 70 moves the feed motor according to an instruction from the CPU 50.

[0029]

As described above, according to the present invention, the following excellent effects can be obtained. Since the maximum displacement amount is calculated based on the displacement of the optical head and the eccentricity amount is calculated from the maximum displacement amount and the phase difference, the eccentricity amount can be accurately calculated by a simple method.

Since the displacement gain and phase are corrected using the eccentricity circuit correction coefficient stored in the ROM on the basis of the cycle of displacement, that is, the number of revolutions of the encoder, the amount of eccentricity can be obtained with high accuracy. it can.

Since the sine waveform is stored in the ROM in advance and the displacement amount is calculated using the sine waveform, the eccentric amount can be easily obtained, and only the maximum eccentric amount and the phase difference can be stored. For example, since the amount of eccentricity can be obtained, the invention can be applied to a device such as a RAM having a small memory capacity.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical head control device to which the present invention is applied.

2 is an enlarged view of an optical head 10 and an encoder 20. FIG.

FIG. 3 is a block diagram illustrating a track servo.

FIG. 4 is a block diagram illustrating a track servo.

FIG. 5 is a diagram showing a processing flow performed when a disc is mounted.

FIG. 6 is a diagram showing signals DS and DSI.

FIG. 7 is a diagram illustrating an eccentricity circuit correction coefficient.

FIG. 8 is a diagram illustrating calculation of a phase difference DIF_PHS.

FIG. 9 is a diagram showing a processing flow of eccentricity correction performed during rough feed.

FIG. 10 is a diagram for explaining a sine waveform table.

FIG. 11 is a diagram illustrating an eccentricity error track number TRACK_VL.

[Explanation of symbols]

 10 Optical Head 11 Disk 20 Encoder 30 Reference Position Detection Sensor 40 Angle Detection Sensor 50 CPU 60 Optical Head Control Unit 70 Feed Motor Control Unit 80 Eccentricity Detection Circuit 90 ROM

Claims (4)

[Claims] 1. An encoder for detecting a reference position and an angle, an optical head control means for controlling an optical head, and a feed motor control means for controlling a feed motor. An optical disk device for performing track servo using optical head control means and feed motor control means,
In the eccentricity measuring method for obtaining the eccentricity amount of the optical disc at a desired angle θ, the displacement amount h of the optical head is measured, and the displacement amount d of the optical disc is d = (1 + F1 / H1) · (1 / F2) · h , H1 is the transfer function of the optical head, F1 is the transfer function of the feed motor, and F2 is the transfer function of the measurement filter, and the first step is calculated; and based on the frequency f of the displacement amount d, The second step of calculating the maximum value Dmax of the displacement amount d, and the phase difference φ between the phase at the zero cross point of the displacement amount d and the phase at the reference position of the encoder are detected, and the eccentricity amount D (θ) And a third step of calculating D (θ) = Dmax · sin (θ + φ). 2. The displacement amount d is calculated by measuring a frequency f of the displacement amount d and using a correction coefficient based on the frequency f in the first step. Eccentricity measurement method. 3. The maximum value Dmax of the displacement amount d is calculated in the second step by obtaining a position where a quarter cycle has elapsed from the zero cross point of the displacement amount d. Eccentricity measurement method. 4. The eccentricity measuring method according to claim 1, wherein in the third step, the eccentricity amount D (θ) is calculated using a sine waveform stored in advance.