JPH0278021A - Recording disk controller - Google Patents

Abstract

PURPOSE:To stabilize rocking at the time of activating a tracking servo regardless of the quantity of eccentricity by detecting the fluctuation ratio of an eccentricity quantity between a guiding track and a pickup scanning locus, and starting a tracking servo operation when the fluctuation ratio becomes smaller than a prescribed value. CONSTITUTION:A tracking error signal detected by an optical pickup 3 is inputted to a tracking servo controller 4, after the controller 4 is activated, the pickup 3 is operated so as to always trace the pickup guiding track. The tracking error signal is inputted to a frequency discriminator as well, its frequencies are discriminated, and the signal at the level corresponding to the frequencies is outputted. Further, it is compared with a prescribed threshold through a differentiator 7 by a level comparator 8, and when it is smaller than the threshold, the controller 4 is activated. Consequently, the rocking at the time of activating the tracking servo is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording disk control device, and more particularly, to a recording disk control device that controls the position of an optical pickup on a substantially circular optical pickup guide track provided on an optical disk substrate.

The present invention relates to a tracking servo control device for controlling.

In a Ryokoji optical disk device, information is recorded and reproduced while a light beam, which is a pickup, follows a guide track, which is a roughly circular guide tank, that is pre-formed on an optical disk substrate. be exposed. This is to make the light beam accurately follow the signal recording track, and this operation is called tracking servo.

Generally, when an optical disk is replaced, it is mounted with an eccentricity that depends on mechanical precision, and the amount of eccentricity differs each time the disk is replaced.

On the other hand, during the tracking servo pull-in operation, the light beam is locked to the shortest recording track with no deviation, so in the transient state from the start of locking to the end of locking, the shortest recording track is It is necessary not to run away from the beam.

In conventional tracking servo control devices, in order to achieve stable retraction of the tracking servo, the rotational speed of the disk is slowed down, or highly accurate machining is performed to keep the amount of eccentricity within an allowable range.

The method of slowing down the rotational speed has the disadvantage that the data transfer rate is slow, and the method of performing high-precision machining has the disadvantage that the equipment is expensive.

Therefore, the present invention was made to solve the drawbacks of the conventional ones, and its purpose is to lock the tracking servo at startup regardless of the size of the concentricity. An object of the present invention is to provide a recording disk control device that can be stabilized.

1. The recording disk control device according to the present invention detects the rate of change in the amount of eccentricity between the guide track and the scanning trajectory of the pickup, which is caused by the eccentricity between the rotation center of the recording disk and the center of the pickup guide track. and means for starting a tracking servo operation when the rate of change becomes smaller than a predetermined value.

Example The present invention will be described in detail below using the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. An optical disk 1 whose rotation is controlled by a spindle motor 2 has signals recorded and reproduced by an optical pickup 3. As shown in FIG. The optical pickup 3 not only records and reproduces the signal, but also detects a focus error signal and a tracking error signal.

The tracking error signal detected by the optical pickup 3 is input to the tracking servo controller 4,
The pickup 3 is operated via the power amplifier 5 so as to always follow the pickup guiding track. The above constitutes a tracking servo loop.

The tracking error signal from the pickup 3 is also input to a frequency discriminator 6, where the frequency is discriminated and a signal having a level corresponding to the frequency is output. This discrimination output is differentiated by a differentiator 7 and then input to a level comparator 8. The level comparator 8 compares the level with a preset threshold, and the comparison output controls the activation of the tracking servo controller 4.

FIG. 2 shows the positional relationship between the rotation center of the optical disk and the center of the guide groove (guide track), which generally has an eccentricity e. At this time, when the tracking servo loop is open, the guide groove shown by the solid line and the scanning locus of the light beam shown by the broken line have a relationship as shown in the figure.

When the optical disk rotates in this state, the tracking error signal is detected as a track pulse that becomes a sine wave with one period each time the light beam crosses the guide groove due to disk eccentricity. Therefore, this track pulse becomes a signal whose frequency is modulated depending on the amount of eccentricity, as shown in FIGS. 3 and 4 (B). In this case, the depth of modulation depends on the amount of eccentricity shown in (A), and the greater the eccentricity, the deeper the modulation.

FIG. 3 shows a case where there is relatively little eccentricity, and FIG. 4 shows a case where there is a relatively large amount of eccentricity.

It can be seen that at points b and d shown in FIG. 2, the guide groove and the light beam cross each other, and the matching portion between them is short, but at points a and 0, the matching portion between them is longer. Therefore, in order to lock the tracking servo, the matching part must be long a
It is a good idea to turn on the servo loop at the 0 point. It is clear that the length of this coincident part depends on the amount of the single core, and that this coincident part can be determined by detecting its rate of change.

Therefore, as shown in FIG. 1, a frequency discriminator 6 discriminates the frequency of the track pulse, which is a tracking error signal when the servo loop is open, to obtain a signal with a level corresponding to the frequency. This signal is, in other words, a signal indicating the amount of eccentricity shown in FIGS. 2 and 3 (A). Therefore, the signal indicating the amount of eccentricity is differentiated by a differentiator 7 to detect its rate of change.

The differential output indicating this rate of change is compared with a predetermined threshold value by the level comparator 8, and when it is smaller than this threshold level, the level comparator generates a timing signal that instructs the servo loop to turn on. If this is done, one tracking servo loop can be turned on at a timing when the rate of change in eccentricity is less than a certain constant.

In Fig. 3.4, the shaded area indicates the rate of change below a predetermined value, and within this range the tracking servo can be locked under the same conditions regardless of the amount of eccentricity.

Although the above description has been made regarding optical discs, it is clear that the present invention can be similarly applied to other recording discs.

As mentioned above, according to the present invention, the tracking servo loop is turned on when the rate of change of the amount of eccentricity is below a certain value, so that the locking at the time of starting the tracking servo is stabilized. In addition, there is an effect that a stable tracking servo loop can be configured regardless of the amount of eccentricity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the guide groove and the scanning locus of the light beam, and FIGS. 3 and 4 are diagrams showing the relationship between the amount of eccentricity and the track pulse, respectively. FIG. Explanation of symbols of main parts 1... Optical disk 3... Optical pickup 4... Tracking servo controller 6...
... Frequency discriminator 7 ... Differentiator 8 ... Level comparator

Claims (1)

[Claims] (1) Means for detecting the rate of change in eccentricity between the guide track and the scanning trajectory of the pickup due to the eccentricity between the center of rotation of the recording disk and the center of the pickup guide track, and a means for detecting a rate of change in the eccentricity between the guide track and the scanning trajectory of the pickup, which is caused by the eccentricity between the center of rotation of the recording disk and the center of the pickup guide track, and the rate of change is greater than a predetermined value. 1. A recording disk control device comprising: means for starting a tracking servo operation when the recording disk becomes smaller.