JP2568525B2 - Runaway prevention device for optical pickup - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for preventing runaway of an optical pickup, and more particularly, to an apparatus for recording and reproducing digital information such as code data, still images, moving images, and sounds on an optical disk. It relates to a device for preventing runaway.

2. Description of the Related Art FIG. 2 shows a general optical disk device having a rotary optical pickup, in which a radial controller 1 can reciprocate along a pair of guide rails 2, and its movable range is usually several tens. mm. A tracking controller 3 is rotatably mounted (rotation angle θ) on a shaft 1 a of the radial controller 1, and an objective lens 4 of an optical pickup is mounted on the tracking controller 3.

When the tracking controller 3 rotates by a small angle, the objective lens 4 moves similarly (usually several tens to several hundreds of μm). Therefore, the objective lens 4 is roughly positioned by the radial controller 1 and is precisely positioned by the tracking controller 3. Is positioned at

The optical pickup irradiates an optical disc (not shown) with laser light to record information, reproduces recorded information by reflected light, obtains a tracking error signal for tracking servo and a focus error signal for focus servo, The tracking controller 3 is controlled by a tracking error signal.

In addition, the control of the conventional radial controller 1 is performed by an external control signal, for example, by providing a detector for detecting the position of the radial controller 1, or the rotation angle θ of the tracking controller 3 is detected. Or a control is performed so that θ = 0 by a tracking error signal.

Problems to be Solved by the Invention However, in the method of controlling the radial controller 1 based on the tracking error signal, since the tracking error signal indicates the amount and direction of the deviation of the track, the tracking error signal is usually used. The controllable deviation is determined within a predetermined range in order to obtain the position periodically, so that when the tracking error signal is obtained by one laser beam, the position control of the objective lens 4 is deviated due to a disturbance or the like. In some cases, the relative speed of the laser spot with respect to the track increases, and when trying to follow this, the control gain of the radial controller 1 increases, causing a problem that the optical pickup goes out of control.

In order to prevent runaway of the optical pickup as described above, the control gain of the radial controller 1 may be reduced. However, if the control gain is forcibly suppressed in this manner, it is necessary to correct a normal tracking error. However, there is a problem that it cannot be made accurate and prompt.

The present invention has been made in view of the above problems, and has as its object to provide an apparatus capable of preventing runaway of an optical pickup even when position control of a tracking controller is deviated due to disturbance or the like in a state where a control gain of a radial controller is high. Things.

Means for Solving the Problems In order to solve the above problems, the present invention forcibly applies a detection signal output when a tracking error amount is detected and the error amount becomes equal to or more than a certain value and a tracking servo such as seek. In this case, it is determined that the tracking error has occurred due to disturbance or the like based on a signal indicating that the tracking control is OFF, and the radial control is turned off by this determination.

Effect of the Invention With the above configuration, the present invention turns off the radial controller when the tracking error signal exceeds a predetermined level, and prevents runaway of the optical pickup in the case of abnormal tracking loss due to disturbance or the like, Even if the tracking signal exceeds a predetermined level, the above-described radial controller is not turned off when the tracking servo is turned off, such as during seek or jumping. If the tracking error signal does not reach the predetermined level, the control gain of the radial controller is the same as that of the conventional device, which outputs and drives an amount corresponding to the position detector from the outside. Can be done.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of an optical pickup runaway prevention device according to the present invention.

The tracking error signal A is obtained by reflected light obtained by irradiating the optical disc with laser light by the optical pickup as described with reference to FIG. 2, and as shown in FIG. This is a signal having a sinusoidal periodicity with a pitch of one wavelength.

When the level of the signal A is “0”, it indicates that the laser beam is being irradiated on the track of the optical disc,
When it deviates from "0", the tracking servo operates,
It is controlled so that the laser beam is always irradiated on the track of the optical disk.

The detection circuit 11 sets the positive and negative peak levels of the tracking error signal A to ± 50%, and outputs a high-level signal when the level of the track error signal A exceeds ± 30%.

To the logic gate 12, the detection circuit 11 sets the positive and negative peak levels of the tracking error signal A to ± 50%, and outputs a high-level signal when the level of the tracking error signal A exceeds ± 30%.

The output signal of the detection circuit 11 is input to the logic gate 12, and a signal indicating a normal state even if tracking is lost, for example, a signal indicating that the tracking servo is off, a track at a predetermined address on the optical disk, A seek signal for searching, a jumping signal for jumping a plurality of tracks in various trick plays, and the like are inverted and input.

A signal indicating that these tracking servos are off, a seek signal for searching for a track at a predetermined address on the optical disk, a jumping signal for jumping a plurality of tracks in various trick plays, etc. It is output from the illustrated control circuit.

The output terminal of the logic gate 12 is connected to a circuit 13 for controlling the tracking of the radial controller, and this circuit 13 is turned off when the signal from the logic gate 12 is at a high level and is turned off as shown in FIG. The radial controller 1 is controlled so that the rotation angle θ becomes “0” when the level is low.

That is, in the present embodiment, the operation of the radial controller 1 is turned off when the tracking error signal A exceeds ± 30% except when the tracking servo is turned off or during trick play such as seek and jumping. This is to avoid the risk of runaway of the pickup. If the tracking error signal A does not exceed ± 30%, the radial controller can move with a control gain externally applied to the position detector, so that accurate tracking can be performed. Further, when the tracking servo is turned off, or during trick play such as seek or jumping, the above-described radial controller 1 is controlled so as not to be turned off, so that the optical pickup can be freely driven without the tracking servo. be able to.

As described above, according to the present invention, a tracking error detection circuit that outputs a detection signal when a tracking error signal indicating a track shift amount and a shift direction exceeds a predetermined setting range, A logic circuit that generates a tracking-off signal from the signal for releasing the tracking servo and the detection signal, and a radial control circuit that performs radial control based on the tracking-off signal. When the amount of the error signal reaches a predetermined level, it is recognized that the track is off the track due to disturbance or the like, and the radial controller is turned off. Therefore, runaway of the optical pickup can be prevented.
If the amount of the tracking error signal does not reach the predetermined level, the radial controller can move with a control gain relative to an external position detector, so that accurate tracking can be performed. It is.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical pickup runaway prevention device according to the present invention, and FIG. 2 is a schematic configuration diagram of the optical pickup device. 1 ... radial controller, 11 ... detection circuit, 12 ... logic gate, 13 ... radial controller.

Claims (1)

(57) [Claims] A tracking error detection circuit for outputting a detection signal when a tracking error signal indicating a track shift amount and a shift direction exceeds a predetermined set range; and a signal for forcibly canceling a tracking servo. A control circuit that outputs a signal, a logic circuit that generates a tracking-off signal from the detection signal and the signal that releases the tracking servo, and a radial control circuit that performs radial control on the optical pickup. Outputting a tracking-off signal when receiving a detection signal from the tracking error detection circuit in a state where a signal for canceling tracking servo from a control circuit is not received, wherein the radial control circuit is The feature is that the radial control is turned off by the tracking loss signal Runaway blocking device of the optical pick-up that.