JPH04232673A - Moving speed detector - Google Patents

Abstract

PURPOSE:To accurately measure the moving speed of an optical head even when the moving speed is high by performing a prescribed arithmetic operation for adjustment when a track crossing pulse is added or deleted. CONSTITUTION:At the time of detecting the moving speed of an optical head by counting track crossing pulses obtained when the optical head crosses the track of a recording medium, a comparison/adjustment circuit 5 performs the addition or deletion of the track crossing pulses. When the track crossing pulses are added or deleted, a difference calculation circuit 6 holds the preceding interval TN-1 as a track cross pulse interval TN and, at the same time, performs adjustmental operations for finding the mean value (TN+TN-1)/2 of the preceding interval TN-1 and current interval TN before adjustment as a track crossing pulse interval TN+1. A speed generation circuit 7 detects the moving speed of the optical head from the operated interval.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving speed detection device for detecting the speed at which an optical head traverses a track on a recording medium.

0002

2. Description of the Related Art In recent years, recording and reproducing apparatuses using disc-shaped recording media as information recording means have been widely used. Optical disk devices that use optical pickups (optical heads) and are capable of high-density recording are also becoming widespread.

[0003] Although this optical disk can perform high-density recording compared to other types of memory, the positioning of the optical head to the target track requires extremely fine control technology compared to other disk-type recording media.

As a seek control method for positioning an optical head to a target track on an optical disk, there is a method for seeking the target track by counting track cross pulses generated when crossing tracks on the optical disk. This method allows reliable positioning in one go.

However, a track on an optical disk is divided into a plurality of information areas (hereinafter referred to as sectors), and at the beginning of each sector there is a circumferential or spiral groove (hereinafter referred to as a groove) for obtaining a track cross pulse. ) is cut off. In this interrupted part, a track address or sector number, etc. is recorded in advance, and a mirror surface part (hereinafter referred to as a mirror mark) is used to remove track offset in the push-pull tracking method.
may be provided.

When an optical head seeks a track on such an optical disk, if a light spot emitted from the optical head passes through an interrupted portion of the groove, track cross pulses are lost, making it difficult to accurately count track cross pulses. The problem was that I couldn't do it.

[0007]

[0006] In the conventional art, the moving speed of an optical head has been detected by measuring the interval between crossing pulses using a counter.

Therefore, since the track crossing pulse interval cannot be accurately measured, it has been difficult to accurately detect the moving speed of the optical head.

To solve these drawbacks, there is a track cross signal counting device disclosed in Japanese Patent Laid-Open No. 1-277378.

[0010] This device compares the interval of the previous track crossing pulse with the interval of the current track crossing pulse, and adds or deletes the track crossing pulse so that the current interval becomes equal to the previous interval. was being carried out. When such pulses are added or deleted, the previous interval is maintained and replaced as the interval between track crossing pulses.

In the case of such an apparatus, when the track crossing pulse is corrected, the next and subsequent track crossing pulse intervals are estimated to be the same as the previous value. Therefore, if the moving speed of the optical head is constant, the optical head operates without problems. However, if the moving speed of the optical head changes rapidly (during rapid acceleration,
(during sudden deceleration), the moving speed of the optical head is estimated by estimating the same track crossing pulse interval as the previous time.
The error becomes larger. This error also affects the next pulse interval.

[0012] Therefore, there is a high possibility that the next track crossing pulse interval will also be incorrect. As a result, there is a problem that the error in speed detection increases.

[0013] The present invention has been made with attention to these points, and its purpose is to improve speed detection even when the track crossing pulse is adjusted when the speed change of the optical head is large. It is an object of the present invention to provide a moving speed detection device that has small errors and is not easily affected by noise and the like.

[0014]

[Means for Solving the Problems] The present invention solves the above-mentioned problems, and the present invention provides a moving speed detection method that detects the moving speed of an optical head by counting track crossing pulses obtained when crossing tracks of a recording medium having tracks. In the apparatus, a measuring means for measuring the track crossing pulse interval, a storage means for storing the previous track crossing pulse interval and the interval difference between the previous time and the previous time;
a comparison means for comparing the previous track crossing pulse interval and the current track crossing pulse interval; an adjustment means for adding or deleting a track crossing pulse according to the comparison result of the comparison means; When deletion is performed, the previous interval TN-1 is retained as the track crossing pulse interval TN, and the previous interval TN-1 is retained as the track crossing pulse interval TN+1.
and the current interval TN before adjustment (TN-1+TN
)/2, and a moving speed detecting means that detects the moving speed of the optical head from the interval between track crossing pulses.

[0015]

[Operation] In the present invention, when detecting the moving speed of the optical head by counting the track crossing pulses obtained when crossing the tracks of a recording medium having tracks, the adjustment means adds or deletes the track crossing pulses. In this case, the previous interval TN-1 is held as the track crossing pulse interval TN, and the track crossing pulse interval TN+1 is maintained.
Then, an adjustment calculation is performed to calculate the average value of the previous interval TN-1 and the current interval TN before adjustment as (TN-1+TN)/2, and the movement of the optical head is calculated based on the track crossing pulse interval obtained in this way. Detect speed.

[0016] As a result, accurate measurement is possible even when the movement speed of the optical head varies greatly.

[0017]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a time chart showing the operation of the configuration shown in FIG.

The operation of this embodiment will be explained in detail below with reference to FIGS. 1 and 2. The track error signal from the optical head is applied to the track crossing pulse generation circuit 1, and is waveform-shaped into a track crossing pulse (
It is output as shown in FIG. 2(a). This track crossing pulse is input to a pulse interval counter 4. This pulse interval counter 4 counts the reference clock while two track crossing pulses are input, and converts the counted value (track interval) into count data (Fig. 2(d)
)) is sent to the difference calculation circuit 6.

On the other hand, the comparison pulse counter that receives the track crossing pulse and the comparison clocks 1 and 2 counts the track crossing pulses based on the comparison clocks 1 and 2, and the comparison pulse generation circuit 3 that receives this counting result counts the track crossing pulses based on the comparison clocks 1 and 2. A comparison pulse is sent to the comparison/adjustment circuit 5 (Fig. 2(b)).
send.

The comparison/adjustment circuit 5 outputs a pulse for correcting when a track crossing pulse is missing. On the other hand, if an extra track crossing pulse is counted, a correction is made to delete one pulse. Normal track crossing pulse corrected in this way (
2(c)) is sent to the speed generation circuit 7. This normal track crossing pulse is also sent to the pulse interval counter 4 as a clear signal.

The difference calculation circuit 6 has a pulse interval counter 4
The track crossing pulse interval difference is calculated based on the count data from the comparator and the additional pulse detection signal from the comparison/adjustment circuit 5.

The speed generation circuit 7 receives the calculation result of the difference calculation circuit 6 (FIG. 2(e)), the additional pulse detection signal, and the normal track crossing pulse, and calculates the speed of the optical head as described later.

Here, the features of this embodiment will be explained in detail with reference to the time chart of this embodiment shown in FIG. 2 and the time chart of the conventional apparatus shown in FIG.

If the track crossing pulse is not corrected, the count data (T0 to T3 in FIG. 2(d)) from the pulse interval counter 4 is sent as is to the speed generation circuit 7 (T0 to T3 in FIG. 2(e)). ~T3). Then, the speed generation circuit 7 determines the moving speed of the optical head. Here, if the inter-track distance is A, then A/T0 to A/T3 are obtained corresponding to T0 to T3 (FIG. 2(f)).

Here, when the addition of a pulse occurs in the comparison/adjustment circuit 5, the difference calculation circuit 6 executes the following difference calculation.

That is, the track interval T4 (before adjustment calculation) when the pulse is added is the previous track interval T4.
Replace with 3. Furthermore, the track interval T5 before the adjustment calculation
is replaced with the average (T3+T2/2) of the previous pre-adjustment track interval T4 and the track interval T3 before the previous adjustment. still,
For this process, the difference calculation circuit 6 holds data on the track intervals of the previous time and the time before the previous time. In other words, when a pulse is added, the track interval TN is changed to TN-
1 and as TN+1 (TN-1+TN
)/2.

Conventionally, the immediately preceding track spacing was used as is, as shown in FIG. 3(e). In such a conventional case, it is effective only when the optical head is moving at a constant speed, and has the disadvantage that a large error occurs when the optical head is accelerating or decelerating. In particular, the next track interval (T5 in Figure 3) after adding the track crossing pulse
contains a large error.

On the other hand, in this embodiment, the interval between the next track to which the track crossing pulse is added is adjusted. As a result, almost accurate track spacing can be obtained even when the optical head is accelerating or decelerating. Of course, accurate values can be obtained even when the optical head is moving at a constant speed. From the calculated track interval (FIG. 2(e)) obtained in this way, the speed generation circuit 7 determines the optical head movement speed with reference to the inter-track distance A.

As described above, according to this embodiment, even when the optical head is moving while accelerating and decelerating, when the track crossing pulse is corrected, the moving speed of the optical head can be accurately adjusted. You can know.

[0031]

As described in detail above, in the present invention, when the moving speed of the optical head is detected by counting the track crossing pulses obtained when crossing the tracks of a recording medium having tracks, the adjusting means When adding or deleting a track crossing pulse, the previous interval TN-1 is maintained as the track crossing pulse interval TN, and the previous interval TN-1 is maintained as the track crossing pulse interval TN+1.
1 and the current interval TN before adjustment, and the moving speed of the optical head is detected from the interval between track crossing pulses thus obtained.

Therefore, when correcting the track crossing pulse, even if the change in the moving speed of the optical head is large, it is possible to provide a moving speed detecting device that has small errors in speed detection and is less susceptible to the effects of noise, etc. .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a time chart showing the operating state of an embodiment of the present invention.

FIG. 3 is a time chart showing the operating state of a conventional device.

[Explanation of symbols]

1 Track crossing pulse pulse generation circuit 2
Comparison pulse counter 3 Comparison pulse generation circuit 4 Pulse interval counter 5
Comparison/adjustment circuit

Claims (1)

[Claims] 1. A moving speed detection device for detecting the moving speed of an optical head by counting track crossing pulses obtained when crossing tracks of a recording medium having tracks, comprising: a measuring means for measuring a track crossing pulse interval; , a storage means for storing the previous track crossing pulse interval and the interval difference between the previous time and the previous time, a comparison means for comparing the previous track crossing pulse interval and the current track crossing pulse interval, and depending on the comparison result of the comparison means. When a track crossing pulse is added or deleted by the adjusting means, the previous interval TN-1 is maintained as the track crossing pulse interval TN, and the track crossing pulse is As the interval TN+1, the average value of the previous interval TN-1 and the current interval TN before adjustment (TN
-1+TN)/2.
A moving speed detecting device comprising: moving speed detecting means for detecting the moving speed of an optical head from the interval of track crossing pulses.