JPH0828082B2 - Tracking Servo Method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a pickup to read a signal recorded on tracks arranged in parallel, so that a signal reading position (spot) of the pickup is on the track. , A tracking servo method for driving a pickup in a direction perpendicular to a track.

2. Description of the Related Art FIG. 3 is a configuration diagram of a portion for reading a recording signal of a compact disc (CD) player, 1 is a cross section of a CD, 2 is a track on which a signal is recorded, and 3 is a pickup. , L = 1.6 μm is the track pitch. The pickup emits a laser beam and at the same time receives the reflected light from the disc surface to generate a tracking error signal corresponding to the amount of deviation between the track and the spot, an on-track detection signal indicating whether the spot is near the track, and a recording signal. read. The tracking drive signal is a signal that drives the pickup in the direction perpendicular to the track. During CD playback, the signal that passes the tracking error signal through an appropriate filter is the tracking drive signal, and the spot follows the track. . The on-track detection signal is recognized as being in the off-track state and becomes the low level when the level of the recording signal is equal to or lower than a preset value, and is otherwise recognized as being in the on-track state and becomes the high level. It is a digital signal.
FIG. 4 is a relationship diagram between the amount of deviation between the spot and the track and the tracking error.

An example of the conventional tracking servo method described above will be described below with reference to the drawings.

FIG. 2 is a waveform diagram of a tracking error signal and a tracking drive signal when a spot is moving across a track by the conventional tracking servo method. In FIG. 2, (a) is a tracking error signal, (b) is a tracking drive signal, B1, B2, and B3 represent periods in the on-track state, and A0, A1, A2, and A3 are in the off-track state. Indicates the period. In the conventional tracking servo method, tracking servo is applied during on-track periods B1, B2, B3, and tracking drive is performed in the off-track periods A0, A1, A2, A3 in a direction that reduces the relative speed of the pickup to the track. The tracking servo is applied when a signal is generated, and the pickup is not driven otherwise.

With the above configuration, even if the pickup is moving at a large relative speed with respect to the track, the tracking drive signal drives the pickup in a direction that reduces this relative speed on average, so that the tracking servo is stable. Can be retracted. (For example, Japanese Patent Publication Sho 59-27973
(Problems to be solved by the invention) However, in the above-mentioned configuration, it is detected that the tracking servo takes too long to pull in and in which direction the pickup is moving with respect to the track. It had a problem that it was necessary.

In view of the above problems, the present invention provides a tracking servo method in which the pull-in time of the tracking servo is short and it is not necessary to detect in which direction the pickup is moving with respect to the track.

Means for Solving the Problems In order to solve the above problems, the tracking servo method of the present invention provides a pickup with a sufficiently large driving force in a direction in which the relative speed of the pickup to the track is automatically suppressed in the off-track state. It has a configuration that occurs.

Action The present invention has the above-described configuration, and the tracking servo pull-in time is short, and it is not necessary to detect in which direction the pickup is moving relative to the track.

Embodiment A tracking servo method according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a waveform diagram of a tracking error signal and a tracking drive signal when a spot is moving across a track by a tracking servo method according to an embodiment of the present invention. In FIG. 1, (a) is a tracking error signal, (b) is a tracking drive signal, B1, B2, and B3 represent periods in the on-track state, and A0, A1, A2, and A3 are in the off-track state. Indicates the period. The present invention is the period of the on-track state.
Tracking servo is applied to B1, B2, and B3, and the tracking drive signal in the off-track period A0, A1, A2, and A3 is the same as the sign of the tracking error signal in the on-track state immediately before the off-track state. It has the opposite sign and is configured so that the absolute value is V (V> 0).
That is, during the off-track state, the tracking drive signal has its own code immediately before the off-track state.

With the above configuration, when the pickup is moving with respect to the track and is in the off-track state, the driving force V automatically acts on the pickup in the direction to stop the movement.

As described above, according to this embodiment, the average force of the servo in the on-track state and the driving force in the off-track state both act in the direction of stopping the movement of the pickup with respect to the track, so that the tracking servo is stably performed. Pull in.

To pull in the tracking servo in a short time, V
Should be increased.

EFFECTS OF THE INVENTION As described above, the present invention can quickly bring in the tracking servo by an extremely simple method, and is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a waveform diagram of a tracking error signal and a tracking drive signal when a spot is moving across a track in a tracking servo method according to an embodiment of the present invention, and FIG. 2 is a conventional tracking servo method. Waveform diagrams of the tracking error signal and the tracking drive signal when the spot is moving across the track, FIG. 3 is a configuration diagram of a portion for reading the recording signal of the CD player, and FIG. 4 is a shift amount between the spot and the track. It is a relationship diagram with a tracking error. 1 ... disk cross section, 2 ... track, 3 ... pickup.

Claims (1)

[Claims] 1. A reference having a reference for determining whether it is an on-track state or an off-track state. In the off-track state, the tracking servo signal is not applied, and a predetermined same sign as the tracking drive signal immediately before the off-track state is set. A tracking servo method characterized in that a pickup is driven by a tracking drive signal having a value V, and tracking servo is applied in an on-track state.