JPH0719384B2 - Optical disk device - Google Patents

Description

The present invention relates to an improvement in accessing an optical head to a medium having a large number of concentric circles or spiral tracks such as an optical disc device.

(Prior Art) Conventionally, in an optical disc device or the like, it is necessary to move an optical head to a predetermined place as fast as possible to reproduce or record. For this reason, the optical head is directly moved by a linear motor or the like for high-speed access. After moving to a predetermined place in these, it is necessary to stop and hold the track of the disk promptly.

(Problems to be solved by the invention) Conventionally, a linear motor is provided with a detector such as a speed detector,
With this, the stop servo is applied. However, there are drawbacks such that the structure becomes complicated due to the addition of a detector and the weight of the moving body increases. Further, in an eccentric disk, it is difficult to stop relative to the track. Therefore, there is a method in which the head moving speed is taken out and stopped depending on the track information of the disk. In this case, it is necessary to know the relative direction with respect to the track, and the direction is detected by two signals having different phases, such as a track error signal and an information envelope signal, and a voltage having a polarity to stop in a predetermined direction is applied. However, in this case, a two-phase signal is required, and an information envelope signal cannot be obtained on a disc such as a writable disc that has not yet been written with data, and only one type of tracking error signal such as a pregroup can be obtained. , The relative direction could not be detected.

(Means for Solving Problems) In the present invention, by using these disks, it is possible to obtain a brake servo capable of maintaining a relative position with respect to a track even with a one-phase signal such as a tracking error signal. To do.

A voltage is applied to a head movement actuator such as a linear motor, the optical head detects the acceleration direction from the time change of the track cross, and a voltage is applied in the direction in which the relative speed decreases with respect to the track so that the stop direction is always maintained. ,
It is configured to perform a braking action after access.

(Embodiment) FIG. 1 shows a block diagram of an embodiment of the present invention. Further, FIG. 2 shows a waveform diagram for explanation. First, the amplifier 1 amplifies a tracking error signal obtained from an optical head (not shown) at the input TE. As the amplified tracking error signal (a), a push-pull signal by a two-division optical detector or the like is known in the case of a one-beam type optical head.
As a result, the group information of the disk is obtained, and if the optical spot is moving relative to the track of the disk, the second
The output is almost sinusoidal as shown in FIG. The waveform shaping circuit 2 converts this into a pulse waveform as shown in FIG. The circuit 2 can be obtained by a slice circuit or a shift circuit. Next, by the counter 3, the waveform (b)
This standard measures the period of the clock, and the clock is obtained from the clock generator OSC12, which consists of a high-frequency oscillator. If the output state of this counter is expressed in analog, it can be expressed as shown in (c). This counter is cleared for each edge of this pulse waveform (b),
Count each time. The shift registers 4 and 5 are provided to latch the data before clearing this counter. The latch 5 becomes the data one pulse before by the latch 4. The difference between the two data thus latched is taken out by the comparator 6 as positive or negative, and the difference signal Δ is inverted as in (c) depending on whether the pulse period is large or small as in (f). This output activates the voltage generation circuit 7,
A negative voltage (g) is generated and applied to the slide feed motor 10 via the power amplifier 9. The direction added here is
When the direction added at the beginning in FIG. 2 is such that the optical head is moving to the right with respect to the track as shown in the figure,
To stop this, when a voltage is applied to move to the left, it acts as a brake, acts relatively in the stopping direction, and then shifts to the left. At this time, the pulse period increases, and it tries to start accelerating to the left again near the time point x.
At this time, the output f of the comparator 6 in which the track pitch cycle moves again in the increasing direction thereafter becomes inverted, and at this time, a reverse voltage is applied from the voltage generator 7 to the motor 10 to drive it in the reverse direction. When relative acceleration is started with respect to the track, the previous reverse pulse is issued again, and thereafter, the cycle is not accelerated again, and a loop is formed so as to always increase the cycle of the track cross. The operation of the loop which stops relatively to this track is operated by the switch circuit 8. This control is performed by the servo control circuit 11. These slide movement and stop commands are conventionally known means such as a micro computer, and the description thereof will be omitted. The state of stopping by sliding will be described with reference to FIG. Now, it is assumed that the optical head is moved by the sliding motor 10 and the stop is started at time y. Now the loop is inserted into the loop by switch 8. A positive or negative voltage is applied when entering the loop. Assuming that a negative voltage is first generated in the direction of the braking action as indicated by the solid line in FIG. 3, the polarities are aligned in the stopping direction and the speed is 0. When the speed exceeds 0 and starts to return in reverse, an alternating voltage z'is applied to the motor 10 so that a positive voltage is generated and becomes 0 after the z point, and the head is held at approximately one point relative to the track, and the head accelerates without fail. There is no runaway. In general, the movement direction before the point y is generally lost because it is moved by a command, and the voltage in this braking direction can be set from the beginning as shown in FIG. If this setting is not performed and the polarity of the start is randomly determined irrespective of the setting, there is a 1/2 probability that the acceleration direction will be the reverse, not the braking direction. At this time, the speed increases due to the reverse voltage once as indicated by the broken line in FIG. Since this increase is detected by the comparator, it is quickly reversed in the correct braking direction, and correct braking occurs. At this time, the track cross frequency is high at the beginning of the stop, so that the pulse period is short and quick judgment is possible. As described above, it is possible to relatively stop the optical head to the target track from any state. After z in FIG. 3, the optical head is in a substantially stopped state, and the servo control 11 controls the switch 8 to control the track. The servo can be inserted after this to perform the next operation, and the linear motor can be used to perform stable braking without the risk of runaway without installing a special detector, and drive the optical pickup to the target track. You can apply a stop servo.
In the above description, the relative acceleration state with respect to the track is detected by the time difference between the track cross periods, but the difference between the cycles at a few tracks may be taken to increase the comparison level. Further, instead of a digital counter, an analog circuit such as an integrating circuit or a sample and hold circuit can be realized, or software processing such as a micro computer can be performed. Although the comparator output has two levels of positive and negative, the voltage applied to the motor may be varied depending on the level of the comparator, that is, the magnitude of the difference signal. This can be realized by adding a D / A comparator, etc. to the comparator output, and a smoother stop can be achieved.

(Effect of the invention) According to the present invention, when the optical head is moved to the predetermined track, the braking force is switched to the direction in which the track cross speed is detected from the track cross signal and converged, and the optical head driving means is applied. Even if the brake force is applied in reverse, the speed is detected and switched to the convergence direction even if the vehicle is accelerated, so it is possible to quickly perform a track search to a predetermined track, and even if the track servo comes off due to noise or scratches on the optical disk. , The increase or decrease in the speed of the track cross is detected to prevent divergence and converge to a predetermined track,
A track servo can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing its waveform, and FIG. 3 is a diagram showing speed and control voltage. 1 …… Amplifier 2 …… Waveform shaping circuit 3 …… Counter 4,5 …… Latch 6 …… Comparator 7 …… Voltage generation circuit 8 …… Switch 9 …… Power amplifier 10 …… Motor 11 …… Servo control 12… ... is an oscillator

Claims (1)

[Claims] 1. A drive means for moving an optical head to a predetermined position of the optical disk for reproducing the optical disk, and a detecting means for detecting a track cross signal from the optical head.
A means for detecting the track cross signal and for moving the optical head to the predetermined position by the driving means; a means for generating a braking force to the drive means near the predetermined position; and a track cross signal for the track cross signal. A means for detecting an increase / decrease in the track cross speed and a means for detecting the increase / decrease in the speed and switching to a direction in which the braking force applied to the driving means is converged are provided, and the track head servos the optical head to the predetermined position. Characteristic optical disk device.