JPH07334947A - Method for detecting track position of optical disk device - Google Patents

Abstract

PURPOSE:To reduce an error in measurement and detection and to move on plural tracks correctly by measuring and detecting speed of scanning disk and disk radius and calculating the number of tracks to move until a target track. CONSTITUTION:The scanning speed V in a certain disk radius R is obtained by V=2piR/T... (number 1). Similarly, the scanning speed Vn in the disk radius Rn is obtained by Vn=piRn/Tn... (number 2). Further, the disk radius Rn is expressed like Rn=R+NP... (number 3) by using the number N of tracks 2 to move from the disk radius R (P: track pitch). Then, since the scanning speed is fixed, when the disk radius R is erased from the number 1 - number 3 by using the relation V=Vs, V=(2pi/Tn-T)NP... (number 4), r=(Tn/Tn-T)NP... (number 5) are obtained. In such a manner, by measuring the rotational period T of the disk 1 in optional two points and the number N of tracks to move between two points, the optional disk radius Rn and the scanning speed V are calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track position detecting method for an optical disk device, which is a method for reading and writing an information signal with an optical head at a scanning speed equal to a linear speed on a disk recorded in a spiral track at a constant linear speed. In particular, the present invention relates to a track position detection method for an optical disk device, which calculates a scanning speed and a disk radius based on a measurement result to calculate a track position.

[0002]

2. Description of the Related Art Conventionally, there is an optical disc reproducing apparatus for reproducing a disc on which a digital signal is recorded. A digital signal is recorded on this disc at a constant linear velocity, and the scanning speed is constant by comparing the sync signal reproduced from the disc with the reference frequency signal (the same as the linear velocity of the disc).
Although the disc is controlled so that the allowable range of the linear velocity is as large as 1.3 m / s ± 7.7%, the error is large when the track position is calculated using the linear velocity. In this regard, Japanese Patent Application Laid-Open No. 61-13481 (high-speed search method for disc reproducing apparatus) discloses a technique for measuring and detecting the scanning speed of a disc and calculating the track position using this scanning velocity.

[0003]

In the above-mentioned known technique, the optical head (which is the same as the pickup) performs a measurement-only operation at the program start position in order to measure and detect the scanning speed of the disk (the same as the linear speed of the disk). Dedicated sensors for recognizing the start position of the program as well as providing them are arranged.

Further, in the known technique, the radius information of the program start position is used as a constant in addition to the scanning speed of the disk for the calculation of the track position, but the radius error is ±
There is 0.4%, which is added as a calculation error of the track position.

The object of the present invention is not to give the optical head a measurement-dedicated operation for measuring and detecting the scanning speed of the disk, not to be specified at the program start position, and to measure and detect the radius information. It is to provide a method for detecting a track position that eliminates an error.

[0006]

SOLUTION: A reproducing means for reading / writing an information signal recorded in a spiral track on a disk at a constant scanning speed, and a rotation of the disk from at least one drive current of the reproducing means. A sinusoidal component generated due to the movement of the center is extracted, a means for detecting the cycle time and the frequency of appearance of the cycle component, and the scanning speed currently being scanned using the cycle time and the frequency of occurrence, And means for detecting the radius of the disk where the track is located and calculating the track position using the result of measurement and detection.

[0007]

The optical disk device targeted by the present invention is a disk exchange type, and the disk center and the rotation center are different each time the disk is exchanged, although there is a degree of difference. As a result, the peripheral speed should change due to this effect during one rotation of the disc. However, since the reproducing means scans the spiral track on the disc at a constant scanning speed, the reproducing means is changed in peripheral speed. The drive current for absorption is added to the drive current for normal operation. Here, the peripheral velocity change due to the rotation center error becomes a sinusoidal component from the geometrical calculation. Therefore, the sinusoidal component is extracted from the drive current, and the cycle time and frequency
If (the same as the wave number) is detected, the track position on the disk can be calculated from the geometric calculation. The reproducing means includes a focus servo means, a tracking servo means, and a disk servo means.

[0008]

FIG. 3 shows an embodiment of an apparatus to which the present invention is applied. Reference numeral 1 denotes a disk in which a signal obtained by eight-to-teen modulation (hereinafter referred to as EFM) of a digitized signal is recorded in the outer circumference direction from the inner circumference of the spiral track. After the disc 1 is mounted in the optical disc device, the disc 1 is supported by the rotating shaft 4 of the disc motor 3 and is driven to rotate. Reference numeral 5 denotes an optical system pickup (which is synonymous with an optical head), and the laser light emitted from the pickup 5 is reflected by the disk 1 and enters the optical system again. This reflected light is detected by an optical sensor built in the pickup 5, and the intensity of the reflected light, which changes depending on the presence or absence of a pit on the disc 1, is converted into an electric signal.

The signal read by the optical sensor of the pickup 5 is amplified by the amplifier 6 and then supplied to the demodulation circuit 7, where it is FEM demodulated. The data bit 192 bits and the error correction bit 64 bits of each frame of the demodulated signal are supplied to the correction circuit 8. Correction circuit 8 is R
The AM9 is used to de-interleave the 256-bit signal, the code error is further detected and corrected, and the time axis corrected digital signal is taken out.

The read signal from the pickup 5 is supplied to the focus servo circuit 17 and the tracking servo circuit 18, and the user's bit from the demodulation circuit 7 is supplied to the microcomputer 19. The focus servo circuit 17 outputs a drive signal 170 to an actuator that displaces the objective lens of the optical system in the pickup 5 according to the read signal and the control signal from the microcomputer 19 to focus the laser beam on the recording surface of the disc 1. To tie. The drive current 171 of the actuator is sent to the microcomputer 19. Tracking servo circuit 18
Detects a tracking error from the read signal, and further outputs a drive signal 180 to an actuator that displaces the laser light emitted from the pickup 5 in the radial direction of the disk 1 in response to a control signal from the microcomputer 19, and the laser light is emitted. The recording track of the disk 1 is automatically adjusted to scan. The actuator drive current 181 is sent to the microcomputer 19.

The radial servo circuit 20 drives the radial motor 21 according to the scanning track information from the tracking servo circuit 18 and the signal from the microcomputer 19 to move the pickup 5 in the radial direction of the disk 1. The disk servo circuit 22 rotationally drives the disk motor 3 in accordance with an error signal obtained by phase comparison between the frame period signal from the demodulation circuit 7 and the clock signal from the microcomputer 19, and the disk 1 is reproduced at a predetermined linear velocity. To adjust automatically. Disk motor 3
Drive current 221 is sent to the microcomputer 19. A signal generated by operating the operation panel 26 is supplied to the microcomputer 19, which controls the operation of the optical disk device. Further, the display signal from the microcomputer 19 is supplied to the display 27 to display the music number and the like.

Next, an operation flowchart relating to the calculation of the track position of the present invention will be described with reference to FIG. When the disc 1 is mounted in the optical disc device, the radial servo circuit 20 is driven and the pickup 5 is moved to the program start position on the inner circumference of the disc. After that, the focus servo circuit, the tracking servo circuit, and the disk servo circuit are activated to drive the respective actuators, and the recording / reproducing operation on the disk 1 is started.

First, in the processing of F10, the driving current of one of the reproducing means, for example, the disk motor 3 is read in the microcomputer 19.

In the subsequent processing of F20, a sinusoidal component is extracted from the drive current read in advance and the cycle time (corresponding to the disk rotation cycle T) and its wave number (corresponding to the number N of moving tracks of the pickup in agreement with the appearance frequency). Is a process for measuring. The process of detecting the cycle time and its wave number from the sine wave component is obtained by setting a threshold value, converting the sine wave into a rectangular wave, and then detecting the cycle time using a clock signal. . The wave number can be obtained by counting rectangular waves.
Alternatively, the peak value may be obtained and the cycle time between the peak values may be detected using a clock signal.

Here, the reason why the drive current of the disk motor 3 includes a sinusoidal component will be described with reference to FIG. FIG. 4 shows a disc 1 and a spiral track 2 recorded on the disc.
FIG. The optical disk device targeted by the present invention is a disk exchange type, and the disk center A and the rotation center B are different each time the disk is exchanged, although there is a degree of difference.
As a result, rotation to one rotation of the disk from P ₁ on the spiral track 2 until the track to move P ₂ center B
The disk radius changes by the amount of movement. Therefore, when the disc is rotated at a constant speed, the peripheral speed changes. On the other hand, in the reproducing means, the track is scanned at a constant scanning speed by the servo control, and therefore the reproducing means absorbs the driving current for absorbing the change in the peripheral speed in addition to the normal operation. Also,
From the geometrical calculation, it is clear that the peripheral velocity change caused by the rotation center error is a sinusoidal component. Further, it is clear that the influence of the movement of the rotation center due to the disc replacement similarly appears in the drive currents of the tracking control system and the focus control system which are other reproducing means. In the focus control system, the influence of surface wobbling at the time of disc replacement is also superimposed.

FIG. 5 is an explanatory view showing the sinusoidal component included in the drive current of the disk motor 3 from the program start point (innermost circumference) to the outer circumference direction. In this example,
P _1, P ₂ on the spiral track 2 in Fig. 4 corresponding to the peak point of the sinusoidal components. Further, in P _n on the outer peripheral side, the time period T between peak points becomes gradually longer. This is due to scanning over the spiral track at a constant scanning speed.

Subsequently, in the processing of F30, the scanning speed V and the disk radius R _n at the current position of the pickup 5 (converted to the disk position) are calculated by using the disk rotation period T and the number of moving tracks N obtained in F20. This is a process of calculating and storing.

The scanning velocity V at a certain disc radius R can be obtained by the equation 1.

[0019]

[Equation 1]

[0020] Here, T: a disk rotation period of the disk radius R V: Like the scanning speed in the disk radius R, the scanning speed V _n in the disk radius R _n Number 2
Can be obtained at.

[0021]

[Equation 2]

[0022] Here, T _n: disk radius R disc rotation period in _n V _n: the scanning speed in the disc radial R _n In addition, the disk radius R _n is as number 3 using a moving track number N from the disc radius R Can be expressed as

[0023]

Equation 3] R _n = R + NP ... (Equation 3) Here, P: track pitch then scanning speed with the relationship V = V _n is constant, erase the disk radius R from a few to several 3 Then the number 4,
Equation 5 is obtained. In this way, by measuring the disc rotation period T at any two points and the number N of moving tracks between the two points, the disc radius R _n and the scanning speed V can be calculated.

[0024]

[Equation 4]

[0025]

[Equation 5]

Next, the operation flow for calculating the number of moving tracks from the current position to the target track position and the disk angular velocity at the target track position, which are required when moving a plurality of tracks at once, will be described with reference to FIG.

First, in the processing of F100, the reproduction mechanism 25
In order to transfer the (pickup and disc motor) to the target track position, the number of moving tracks N _s from the current position to the target track position and the constant of the current position and the track pitch P required for calculating the disc angular velocity ω _{s at} the target track position. Is a process for setting.

The subsequent process of F110 is a process of setting the reproduction time (corresponding to the time address t ₂ ) from the program start time corresponding to the absolute address of the disk 1 to the target track position.

The subsequent process of F120 is a process of calculating the number of moving tracks N _s from the current position to the target track position. For example, _assuming that the current position is the disk radius R and the target track position is the disk radius R _n , the relationship of equation 6 is obtained from the relationship between the reproduction time and the incremental amount of the disk radius when moving on the spiral track at a constant scanning speed V. Is obtained.

[0030]

[6] _{^{πR n 2 -πR 2 = PV (}} t 2 -t 1) ... ( 6) where, P: track pitch V: scanning speed (constant irrespective of the disk radial) t _2: the target track position Time address t: Time address of current position Next, the disk radius R _n is erased by using Equations 3 and 6,
When the number of moving tracks N _s is solved, the following equation 7 is obtained.

[0031]

[Equation 7]

Where P: track pitch V: scanning speed (constant regardless of disk radius) t ₂ : time address of target track position t: time address of current position R: disk radius of current position The number N _s of moving tracks from the time address of the position and the time address of the current position to the target track position can be calculated. Here, the disk radius at the current position and the scanning speed are calculated based on the measurement results.

The subsequent process of F130 is a process of calculating the disk angular velocity ω _s at the target track position. For example, _assuming that the current position is the disk radius R and the target track position is the disk radius R _n , the increment of the disc angular velocity ω _s has a relationship proportional to the increment of the disc radius.
Is solved to obtain Equation 8.

[0034]

[Equation 8]

Where P: track pitch V: scanning speed (constant regardless of disk radius) t ₂ : time address of target track position t: time address of current position ω: disk angular velocity of current position The disk angular velocity ω _s at the target track position can be calculated from the time address of the position and the time address of the current position. Here, the disk angular velocity and the scanning velocity at the current position are calculated based on the measurement result.

In the subsequent processing of F140, the reproducing mechanism 2 is used by using the number of moving tracks N _s from the current position to the target track position and the disk angular velocity ω _{s at the} target track position.
This is a process of moving 5 to the target track position. Here, the radial servo circuit 20 is the microcomputer 1
The radial motor 21 is driven according to the signal from 9 (corresponding to the movement of a plurality of tracks) and the scanning track information from the tracking servo circuit 18 to move the pickup 5 in the radial direction of the disk 1. Further, the disk servo circuit 22 is provided with a drive signal for shifting the disk angular velocity from ω to ω _s , in addition to the drive signal for scanning at a normal constant scanning speed.

By the above processing of F100 to F140, it becomes possible to move the plurality of tracks more correctly.

[0038]

As described above, since the scanning speed of the disc and the disc radius are measured and detected, and the number of moving tracks to the target track (given by the reproduction time from the program start position) is calculated, the calculation accuracy is improved. Furthermore, the method for measuring and detecting the scanning speed of the disk can be performed at any place without being limited to the program start position without giving the optical head (which is synonymous with the pickup) a dedicated operation for measurement. Therefore, the error in measurement detection is reduced. Further, since the disc angular velocity information on the target track of the moving destination is obtained, it becomes possible to pull the reproducing mechanism (disc control system) to the target angular velocity faster.

[Brief description of drawings]

FIG. 1 is a flowchart showing the overall configuration of the present invention.

FIG. 2 is a flowchart showing another configuration of the present invention.

FIG. 3 is a block diagram of an embodiment of an apparatus to which the present invention is applied.

FIG. 4 is an explanatory diagram showing a spiral track on the disc and a center of rotation of the disc.

FIG. 5 is a sine wave diagram generated in the drive signal of the disk servo circuit.

[Explanation of symbols]

1 ... Disc, 2 ... Spiral track, 3 ... Disc motor, 5 ... Pickup, 6 ... Amplifier, 7 ... Demodulation circuit, 8
... correction circuit, 9 ... RAM, 17 ... focus servo circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mantetsu Soma 111 Nishiyote-cho, Takasaki-shi, Gunma General Computer Division, Hitachi, Ltd.

Claims (1)

[Claims] 1. A track position detecting method for an optical disc apparatus, wherein a disc in which an information signal is recorded on a spiral track at a constant linear velocity is read or written by an optical head at a scanning velocity equal to the linear velocity. Using at least one drive current of the means, to detect the cycle time and the frequency of appearance of the cycle component from the sinusoidal component generated in the drive current due to the movement of the rotation center of the disk, the cycle time A method for detecting a track position of an optical disk device, wherein the scanning speed of the disk and the radius of the disk at which the currently scanned track is located are calculated using the occurrence frequency.