JP3132147B2 - Tracking state detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection circuit for detecting that tracking of an optical disk has reached a retracted state.

[0002]

2. Description of the Related Art A magneto-optical disk for data storage requires high-speed access. In the magneto-optical disk access algorithm, after detecting that the tracking servo has been pulled in stably, the operation proceeds to the next write operation or the like, so that the detection of the pull-in state greatly affects the access speed.

FIG. 5 illustrates a conventional access operation using a tracking error signal TE. The tracking error signal TE can be formed, for example, by calculating four output signals of a quadrant detector irradiated with a reflected beam from the disk. A period indicated by Ta is a seek operation, that is, a period during which the pickup moves in the disk radial direction at high speed. When the tracking servo is turned on at time t0, a tracking servo drive signal is formed from the tracking error signal TE, and the drive signal displaces the spot of the pickup in the tracking direction. The state is located above, that is, the tracking servo is pulled in. And t2,
At the time points indicated by t3 and t4, if the sector of the track is continuously detected, it is determined that the retracted state has been reached at t4. Therefore, the pull-in state is detected after the elapse of the waiting time Tb after the tracking servo is turned on.

[0004]

In the conventional pull-in state detection method, since it is necessary to continuously detect sectors, it is indicated by Tc from the time of the actual pull-in state until the detection thereof. There is dead time. This hinders high-speed access. On the other hand, if the waiting time is too short, the tracking servo system may become unstable during a write or read operation after a seek.

Accordingly, it is an object of the present invention to provide a tracking state detecting circuit which makes it possible to shorten the time required to detect the pull-in of a tracking servo as much as possible and to enable high-speed access.

[0006]

Means for Solving the Problems of claims 1 invention, the target
Performs a seek operation on the track, and
Turn on the button to track the target track
Sometimes, a tracking state detection circuit for detecting the tracking servo has reached the retracted state by using a tracking error signal, and integrating means for integrating the absolute value of the tracking error signal, a fixed amount from the integration output of the integration means and means for subtracting, comparing the integrated output with a threshold value after the subtraction is tracking state detecting circuit comprising a means for determining that led to pull come inclusive state.

[0007]

The tracking error signal becomes a substantially sine wave when crossing a plurality of tracks during a seek, and when approaching the target track, the frequency is reduced.
It becomes a constant value. The pull-in is determined by detecting the change in the tracking error signal.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a tracking error signal S 1 is supplied to an input terminal indicated by 1, supplied to a full-wave rectifier circuit 2, and an output signal S 2 of the full-wave rectifier circuit 2 is supplied to an integration and subtraction circuit 3. This circuit 3 has an operational amplifier 4, input resistors 5, 6 and a capacitor 7 inserted in a feedback path between an output terminal and an inverting input terminal. DC voltage V
Is supplied.

The monitor signal S3 obtained at the output of the integration and subtraction circuit 3 is supplied to a comparator 9 and compared with a threshold value α. The judgment output S4 is extracted from the comparator 9 to the output terminal 10. This judgment output S4
Is seen by the system controller, and when the system controller finds that the pull-in operation has been performed from the determination output S4, the system controller performs control to start a write operation or a read operation.

FIG. 2 is a waveform diagram of each part of an embodiment of the present invention. The tracking error signal S1 is a full-wave rectifier circuit 2.
To form a full-wave rectified output S2 as shown. The tracking error signal S1 has a sine wave shape during a seek, and its frequency decreases as it approaches the target track, and becomes substantially constant when the pickup reaches the target track. The output of the full-wave rectifier circuit 2 is supplied to the integration and subtraction circuit 3, and the output signal S3 is a dashed waveform obtained by subtracting the DC voltage V from the solid-line integrated output in FIG. . In the comparator 9, at time t1 when the output signal S3 of the circuit 3 becomes smaller than the threshold value α, the pull-in of the tracking servo is detected.

In the integration and subtraction circuit 3, the detection of the pull-in is accelerated by the value of the constant voltage V to be subtracted,
Alternatively, it is possible to adjust the delay. Further, since the constant voltage V is subtracted, the output signal S3 of the circuit 3 converges toward the minimum value. If this subtraction is not performed and only integration is performed, the integrated output may not easily reach the minimum value in some cases.
There is a problem that settings are subtle. In this regard, it is advantageous to subtract the constant value V.

FIG. 3 is a conceptual block diagram of another embodiment in which the present invention is constituted by software. Input terminal 1
The tracking error signal S1 from the A / D converter 11
Is converted into digital data. This data is supplied to the decision block 13 in the system controller 12. The system controller 12 is configured by a microcomputer, and the determination block 13 is realized by software shown in a flowchart of FIG.

In FIG. 4, a tracking error signal is input (step 21), and in the next step 22, its absolute value is calculated, and the absolute value is used as data B. Forming the absolute value corresponds to full-wave rectification. Then, in step 23, data B is added to the monitor, and the added output is data A. This addition corresponds to an integration process.

In a step 24 following the addition step 23, A-F (F: constant value) is subtracted, and the subtraction output is monitored. This monitor is compared with α (step 25). If monitor ≧ α, it is determined that settling is being performed (step 26), and the process returns to step 21. If monitor <α, it is determined that tracking is OK (step 27), and detection of pull-in is completed. A series of flows from step 21 to step 26 (or 27) is A /
This is performed at the sampling cycle of the D converter 11.

[0015]

According to the present invention, since it is not necessary to continuously detect sectors, useless waiting time can be almost eliminated, and high-speed access can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the embodiment.

FIG. 3 is a conceptual block diagram of another embodiment of the present invention.

FIG. 4 is a flowchart of another embodiment of the present invention.

FIG. 5 is a waveform chart for explaining a conventional tracking state detection circuit.

[Explanation of symbols]

 1 tracking error signal input terminal 3 integration and subtraction circuit 9 comparator

Claims (1)

(57) [Claims] A seek operation is performed on a target track.
Turn on the tracking servo and turn on the target track.
A tracking state detection circuit for detecting that the tracking servo has reached a retracted state using a tracking error signal when performing tracking, an integrating means for integrating an absolute value of the tracking error signal; said means for subtracting a predetermined amount from the integrated output of the integrating means, compares the integrated output with a threshold value after the subtraction, a tracking state detection circuit comprising a means for determining that led to pull come inclusive state.