JPH0554401A - Track accessing device for optical disk device - Google Patents

Abstract

PURPOSE:To prevent miscounting and to interpolate an omitted pulse by providing a target speed signal or a window at a track crossing pulse cycle at previous two times. CONSTITUTION:When an optical head 5 is driven based upon the target speed signal of a target speed generator 1, a counting device 6 obtains the pulse number of a track crossing signal and supplies it to a pulse count correcting device 8. A window setter 3 sets the window of a specified width at a target speed signal or the track crossing pulse cycle of previous two times and supplies it to the device 8. The device 8 provides a window with the value set by the setter 3, and then shuts off external noises, etc., and if no pulse is detected in the window, corrects the count number as a mirror part. A comparing circuit 10 compares the corrected track pulse number with a target track number, and if coincidence exists, stops moving the optical head. As a result, positioning is precisely performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track access device in an optical disk device, and more particularly, even if a count error occurs in a track cross pulse due to a preformatted signal or a scratch on the disk, the track access pulse is adjusted according to the target access speed at this time. , Or using the previous two cycles of the track pulse,
The present invention relates to a track access device in an optical disk device in which a window is provided for a track cross pulse to prevent miscounting and correct the count value.

[0002]

2. Description of the Related Art Conventionally, there are the following techniques of this type. (1) As disclosed in, for example, Japanese Patent Application Laid-Open Nos. 1-155576 and 1-155577, when a spot passes through a groove-free region (mirror portion) during track access, a track cross pulse is generated. There is a method of inserting an average frequency and interpolating.

(2) A method of correcting one track pulse when the cycle of the track cross signal in the preformat signal becomes 1.5 times or more [1989, Autumn, Japan Society of Applied Physics (30)
a-PB-17)].

(3) A method of using a speed adaptive filter for switching characteristics according to the moving speed in order to remove noise due to addresses and the like [Matsushita, Technical Report Vol3
5, No2 1989 (P67-)].

[0005]

However, these conventional examples have the following drawbacks. In the case of (1), it is necessary to detect the mirror section (preformat section) in advance. This is not easy to detect unless tracking servo is applied.

In the case of (2), the condition for interpolating the track cross pulse is not sufficient. For example, it is necessary to change the interpolation condition when moving at a constant speed and when moving at an acceleration.

In the case of (3), it is impossible to interpolate the lack of the track pulse due to the mirror portion or the like simply by removing it with a filter.

The present invention has been made in view of the above points, and even if there is a scratch or preformat during track access of an optical disk, it can be accurately performed without miscounting tracks, and miscounting can be corrected in real time. However, it is an object of the present invention to provide a track access device that can shorten the access time because accurate positioning can be performed.

[0009]

In order to solve the above problems, the present invention provides a device for generating a target speed signal according to a target track, a head moving circuit for moving an optical head based on the target speed signal, and an optical head. Is a track access device for an optical disc device which detects a position on a disc from a track cross signal detected when a track crosses a track and positions a head position. A window is provided at the track cross pulse period to prevent miscounting, and when the track cross pulse is missing, the number of pulses is interpolated.

[0010]

In the optical disk device, it is general to perform the track cross pulse indicating that the light spot has crossed the track at the time of accessing the track. A count error occurs in the pulse due to a preformatted signal or a scratch on the disc. At this time, a window is provided in the track cross pulse according to the target access speed or by using the previous two cycles of the track pulse, so that the track is miscounted even if there is a scratch or preformat during the track access of the optical disk. It is possible to accurately perform the operation without shortening the access time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a track access device of an optical disk device according to the present invention. As shown in the figure, the track access device counts the device 1 for generating a target speed according to a target track, a head moving circuit 4 for moving an optical head 5 based on the signal, and a track pulse detected by the optical head 5. A counting device 6, a speed detector 7 that detects the moving speed of the optical head based on the count signal, a comparison circuit 9 that compares the speed with a target speed, and a window setting device 3 that sets a window obtained from the target speed. A pulse count correction device 8 that applies a window to the count value to remove noise and corrects missing pulses, and a comparison circuit 10 that compares the target track number with the corrected track pulse number. The chain line in FIG. 1 can be realized by a high-speed CPU.

In the apparatus constructed as shown in FIG. 1, the target speed signal is generated from the target speed generator 1 according to the setting of the target track. The optical head 5 is driven based on this target speed signal and moves in the radial direction on the optical disk surface. Along with this, track cross signals as shown in FIGS. 2 and 3 are detected. FIG. 2 shows the waveform of the track cross signal when the movement of the optical head 5 is a constant velocity movement, and FIG. 3 shows the waveform of the track cross signal when the movement of the optical head 5 is a deceleration movement. Further, when the track cross signal is not detected by the mirror portion or the like in this signal, the waveform of the track cross signal is often as shown in FIG.

The number of pulses of this track cross signal is obtained by the counting device 6, and the pulse count correcting device 8 performs the following operation. It is possible to predict the pulse by measuring each cycle and applying a window with the value set by the window setter 3.

As shown in FIG. 5, the previous pulse widths T ₁ , T ₂ ,
Alternatively, a target speed window is set, and noise and the like outside the target speed window are blocked. When no pulse is detected in the window, the pulse is corrected by the mirror unit and added to the pulse count number.

The comparator circuit 10 compares the corrected number of track pulses with the target number of tracks, and when they match, the movement of the optical head is stopped.

Next, window setting will be described. (1) When using target speed FIG. 6 is a diagram showing an example of a moving speed pattern of the optical head at the time of access. As shown in the figure, the target speed is generally trapezoidal at the time of access. Therefore, let us consider the case of constant velocity movement and the case of constant acceleration movement.

I) When moving at a constant speed The frequency of the track cross is constant. Therefore, Win
The dough is, for example, ± 20% of the previous cross pulse period. ii) When moving at constant acceleration, set the target speed to V for tracks N and N + 1._NAnd V_{N + 1}When
To do. Track pitch is P, track cross signal cycle
Is T_N= P / V_N  T_{N + 1}= P / V_{N + 1}  ∴T_{N + 1}/ T_N= V_N/ V_{N + 1}

Here, the target speed is known in advance. Therefore, the window for _{N + 1} is T _{N + 1} = (1 ± ΔT)
V _N / V _{N + 1} T _N ΔT is, for example, ± 30% although the window width depends on the design of the servo system.

(2) Method Using Two Preceding Cycles of Track Pulse As shown in FIG.₁, T₂And T₂/ T₁Is one
Assuming that it is constant and setting the tolerance, T₃Predict. T₂/ T₁≈T₃/ T₂  And T₃≒ (1 ± ΔT) ・ T₂/ T₁・ T₂  The window width is ± ΔT. However, 2 cycles or more
You may use.

However, if the processing speed of the CPU cannot be met in these calculations, it is necessary to devise to process the data collectively for several cycles (for example, eight cycles). When it is necessary to continuously correct, the predicted value is used for further correction.

[0021]

As described above, according to the present invention, even if there is a scratch or pre-formatting during track access of an optical disk, it can be accurately performed without miscounting tracks and the miscount can be corrected in real time. ,
Since accurate positioning can be performed, an extremely excellent effect of shortening access time can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a track access device according to the present invention.

FIG. 2 is a diagram showing a track cross signal when the optical head moves at a constant speed.

FIG. 3 is a diagram showing a track cross signal during deceleration movement of an optical head.

FIG. 4 is a diagram showing a track cross signal when there is a mirror section.

FIG. 5 is a diagram showing a setting example of previous pulse widths T ₁ and T ₂ or a target speed window.

FIG. 6 is a diagram showing an example of a speed pattern during access.

FIG. 7 is a diagram showing an example of setting a window using the previous two cycles T ₁ and T ₂ .

[Explanation of symbols]

 1 Target Speed Generator 3 Window Setting Device 4 Head Moving Circuit 5 Optical Head 6 Counting Device 7 Speed Detector 8 Pulse Count Correcting Device 9 Comparison Circuit 10 Comparison Circuit

Claims (1)

[Claims] 1. A device for generating a target speed signal according to a target track, a head moving circuit for moving an optical head based on the target speed signal, and a disk from a track cross signal detected when the optical head crosses a track. A track access device for an optical disk device that detects an upper position and positions a head position, wherein a window is provided at a target speed signal or two previous track cross pulse periods to prevent miscount when the track cross pulse is detected. In addition, a track access device for an optical disk device, wherein the number of pulses is interpolated when a track cross pulse is missing.