JPH09204746A - Disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately count the number of tracks by fractionalizing a rectangular pulse outputted from a comparator and forming a track counting pulse in a prescribed position among individual fractionalized pulses respectively as a trigger. SOLUTION: The rectangular pulse outputted from the comparator 5 having a prescribed slice level is supplied to a short pulse generator 6 to generate the fractionalized pulse. The fractionalized pulse is supplied to a regulated time length pulse generator 7, where the track counting pulse is formed in the prescribed position of the fractionalized pulse as the trigger. The track counting pulse formed in this way is also supplied to an access control circuit 10, and the exact number of tracks to be traversed is detected. Thus, by fractionalization of the on-track pulse in the short pulse generator 6, in either case of traversing tracks on a disk 1 by a head means at low speed or high speed, the exact number of tracks can be counted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc for reading recorded information from a pit train or the like recorded circumferentially on a disc-shaped recording medium by a head means such as an optical pickup and converting the recorded information into an electric signal for reproduction. The present invention relates to a device, and particularly to a recording track counting method.

[0002]

2. Description of the Related Art As one of recording track counting methods in a disk device, there is an envelope detection method. In this system, when the pickup crosses over a track, for example, as shown in FIG. 6A, an output signal that undergoes amplitude modulation depending on the presence or absence of the track is obtained. Although it is generally used at present, the track crossing signal component (FIG. 6B) obtained by detecting the envelope of this signal is compared with a predetermined slice level, or the track crossing signal component is integrated. The track count signal (FIG. 6 (c)) is obtained by comparison with the above.

In the pulse length detecting method as shown in Japanese Patent Publication No. 63-191380, the recording information signal is compared at a certain slice level as shown in FIG. A rectangular pulse corresponding to 0 and 1 of the information signal is generated (on-track pulse: FIG. 7B), and this is used as a specified length pulse (maximum bit length of 2).
This is a system for obtaining a track count signal (FIG. 7 (c)) by using it as a trigger of a re-trigger-acceptable pulse generator that generates a double count).

[0004]

However, in the above-mentioned envelope detection method, the element of the low-pass filter is always included when detecting the envelope, and the track count frequency approaches the signal frequency. In such high speed counting, there is a problem that it is difficult to detect a stable track crossing signal component.

Further, the pulse length detection method is more advantageous than the envelope detection method described above for track counting during high-speed crossing, but as shown in FIGS. Occurrence of the on-track pulse near the slice level is not stable in the track count at the time of crossing due to the variation in the signal output, and the pulse may be lost during the on-track pulse. As a result, chattering occurs in the count pulse in FIG. 8C.

Although this pulse length detection method is more advantageous in track counting during high-speed crossing than the above-mentioned envelope detection method, for example, as shown in FIG.
Even in the ideal pulse state as shown in (b), the countable frequency is less than 100 KHz, which is not satisfactory. Generally, the track count pulse is generated as a pulse having a predetermined width (specified length) based on the rising edge of each pulse, but if the interval between the pulses is too short (for example, the width indicated by d ₁ in FIG. 9B), The predetermined width (specified length) becomes longer, and the track count pulse corresponding to each pulse cannot be generated. In the case of EFM modulation, the time margin until re-triggering (rise time until the next pulse) is 22T = 5.0.
It is 9 μsec, and this double is the upper limit of the countable frequency.

Therefore, an object of the present invention is to provide a disk device which solves the above problems.

[0008]

The present invention has been made in view of the above problems, and includes means described in 1) to 3) below. That is, 1) The head means reproduces the recorded information from the track on which predetermined information is recorded by the pits arranged in the circumferential direction on the disk or the change of the magnetic pole direction, and the head means traverses the track. A rectangular pulse is generated by comparison with a predetermined reference level based on a signal modulated accordingly, and a track count pulse of a predetermined length is generated by using a predetermined position of each rectangular pulse as a trigger, and these track count pulses are counted. In the disk device configured to detect the number of traversing tracks, a relative hysteresis is provided in the comparison between the signal modulated according to the traversing of the tracks and the predetermined reference level when the rectangular pulse is generated. And compare each of the pulses that are modulated as they traverse the track. A disk device, characterized in that a track count pulse is formed by using a predetermined position of each of these subdivided pulses as a trigger.

2) The disk device according to claim 1, wherein the relative hysteresis is such that the gain of the output signal of the head means is changed according to the presence or absence of the track count pulse. apparatus.

3) The disk device according to claim 1, wherein the relative hysteresis is set so that the predetermined reference level is changed according to the presence or absence of the track count pulse.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to preferred embodiments. FIG. 1 is a schematic block diagram of a disk device according to the embodiment, and FIG.
It is a waveform diagram in each place in the block.

In these figures, 1 is, for example, EF
This is a disc according to a well-known form in which M-modulated predetermined information is recorded as a pit row in the circumferential direction, and the maximum pit length is 2.55 μsec. This disc 1
A predetermined information signal is read by scanning the pit row by the laser light emitted from the pickup 3 which is rotated by the spindle motor 2 through a servo circuit having a well-known structure (not shown). That is, the presence or absence of the pit is detected by the intensity of the reflected light applied to the pit to read the information.

In this case, if the loaded disc is a music CD, the disc rotation speed is controlled to be a constant linear velocity. Therefore, in the search from the outer circumference to the inner circumference, the spindle mode is adjusted according to the position of the pickup. -It is necessary to increase the rotation speed of the motor. That is, when the pickup 3 is moved to the inner circumference with the rotation speed at the outer circumference being kept, the maximum bit length becomes longer as the pickup 3 moves to the inner circumference.

When the pickup 3 crosses a track, the signal read by the pickup 3 (see FIG. 2).
(A)) is supplied to a comparator 5 having a predetermined slice level after passing through an amplifier 4 having a predetermined amplification factor, and as shown in FIG. 2 (b), a pit row is provided only during on-track. The on-track pulse corresponding to is extracted.

Next, this rectangular pulse is supplied to the short pulse generator 6 to generate a subdivided pulse as shown in FIG. 2 (c). Then, the subdivided pulse is supplied to the prescribed time length pulse generator 7, and here, each rising edge of the subdivided pulse is used as a trigger to generate a pulse of a prescribed length (regulated time length). At this time, the prescribed time length pulse generator 7 receives a re-trigger during pulse generation, so that a pulse as shown in FIG. 2D, for example, is generated. In the pulse shown in the figure, the period of d _{2 is} the pulse of the predetermined length (specified time length), and the number of tracks is detected by detecting the presence or absence of the pulse of the specified length (specified time length). The pulse shown in FIG. 2D becomes the track count pulse.

In the short pulse generator 6 described above, the on-track pulse is subdivided, which makes it possible to shorten the time until the re-trigger is applied. As a result, the specified length pulse time can be halved. That is, when the pulse width is long as shown in FIG.
Although it is possible to detect only a signal loss that is at least twice the maximum bit length, it is possible to detect a signal loss up to approximately the maximum bit length by shortening the pulse width as shown in FIG. 3B. In this case, the track count frequency band is as shown in FIG.
It is almost doubled as compared with (a).

Here, in such an apparatus, the important point in counting the number of tracks accurately is, of course, once the pickup 3 is on-tracked.
If the comparator 5 starts outputting a rectangular pulse,
Pickup 3 goes off track (off track)
There must be no signal loss.

On the contrary, if the pickup 3 goes off the track and the comparator 5 stops outputting the rectangular pulse, an unnecessary signal should not appear until the pickup 3 is next on-tracked. If these conditions are not observed, chattering as described above will occur when the final track count pulse is generated.

The pickup 3 actually used is
At the time of reading the signal, there are fluctuations in the output level and the magnitude of the output due to the length of the bit (due to an optical factor), so the above-mentioned problem is concerned. Therefore, in the apparatus of the embodiment of the present invention, the problem is solved by providing the gain changeover switch 8.

The switching of the gain is performed by the high level and low level of the track count pulse. When the pickup 3 is on-track, the gain of the output signal is increased at the same time when the track count pulse of FIG.
A small level signal shown by the solid line in (a) that does not originally reach the slice level is amplified to a level enough to reach the slice level as shown by the chain line so that an on-track pulse with no omission can be generated. (See FIGS. 4 (b) and 4 (c)).

The same applies when the pickup 3 moves away from the track. At this time, if the gain is made small at the same time as the trailing edge of the track count pulse, the generation of unnecessary pulses until the pickup 3 is next on-tracked can be prevented. .

The track count pulse generated by devising in this way is output from the specified time length pulse generator 7 and supplied to the gain switcher 8 and also to the access control circuit 10. In the access control circuit 10,
Count this incoming track count pulse,
Pickup drive circuit 11 up to a predetermined count number
Through this, the pickup 3 is moved, and when the count numbers match, the movement of the pickup 3 is stopped.

In the above-described embodiment, the gain level is switched according to the level of the track count pulse. However, as shown in FIGS. 5A to 5D, the level of the track count pulse is changed. The comparator may be switched to the levels A and B accordingly.

As described above, according to the apparatus of this embodiment,
The shorter the maximum bit length is, the wider the count band is, and the faster the rotation of the disk is, the more the effect is obtained.

When the 3 beam method is used for tracking servo, a signal having a 90 ° phase shift can be generated, so that the counting including the traveling direction can be performed by a known technique. It is possible.

Further, in the above-mentioned embodiment, the optical head is used, and the disk mounted thereon is also a disk of a known form in which pit rows utilizing light reflection are arranged. However, the present invention is not limited to this, and a magnetic head is used. Of course, even if the disc mounted thereon is a disc in which predetermined information is recorded by the change of the magnetic pole direction, the above-mentioned configuration can be applied.

[0027]

According to the present invention, the number of tracks can be accurately counted regardless of whether the head means traverses the track at a low speed or at a high speed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a disk device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram at various points of the disk device according to the embodiment of the present invention.

FIG. 3 is a diagram for comparing a track count pulse in the conventional device and a track count pulse in the device according to the present embodiment.

FIG. 4 is a diagram showing a process of generating a track count pulse when gain switching is performed.

FIG. 5 is a diagram showing a process of generating a track count pulse when the slice level of the comparator is switched.

FIG. 6 is a waveform diagram for explaining a conventional envelope detection method.

FIG. 7 is a waveform diagram for explaining a conventional pulse length detection method.

FIG. 8 is a waveform diagram for explaining variations in output when the disc rotates at a low speed.

FIG. 9 is a diagram for explaining the relationship between a track count pulse and a specified length pulse.

[Explanation of symbols]

 1 Disc 2 Spindle Motor 3 Pickup 4 Amplifier 5 Comparator 6 Short Pulse Generator 7 Specified Time Length Pulse Generator 8 Gain Switcher 10 Access Control Circuit 11 Pickup Drive Circuit

Claims (3)

[Claims] 1. A head means reproduces recorded information from a track on which predetermined information is recorded by pits arranged in the circumferential direction on a disk or a change in magnetic pole direction, and the head means traverses the track. A rectangular pulse is generated by comparison with a predetermined reference level based on a signal modulated in accordance with, a track count pulse of a predetermined length is generated by using a predetermined position of each rectangular pulse as a trigger, and these track count pulses are counted. In the disk device configured to detect the number of traversing tracks by the above, when the rectangular pulse is generated, a relative hysteresis is provided in the comparison between the signal modulated according to the traversing of the tracks and the predetermined reference level. And compare each of the pulses that are modulated as they traverse the track. And a track count pulse is formed by using a predetermined position of each of these subdivided pulses as a trigger. 2. The disk device according to claim 1, wherein
A disk device, wherein the relative hysteresis is adapted to change the gain of the output signal of the head means according to the presence or absence of the track count pulse. 3. The disk device according to claim 1, wherein
The disk device, wherein the predetermined reference level is changed in accordance with the presence or absence of the track count pulse for relative hysteresis.