JPS63237223A - Optical disk recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a focus servo from being locked off when the tracking servo is turned off by operating a blind sector gate circuit in which a focus servo circuit is provided at the time of track seeking or when the tracking servo is turned off. CONSTITUTION:The output of an photoelectric element PD is inputted to a focus error detection circuit 11, and focus error signals are outputted, whereby they are inputted to a drive coil 17 through a pre-amplifier 12, the blind sector gate circuit 13 a phase compensation circuit 15 and a focus drive circuit 16. When the tracking servo is turned off, the signals of an H level are inputted to a terminal C1, and the output of a differential amplifier OP is deteriorated, whereby a switch S is opened. The circuit 13 attenuates traverse signals which are overlapped with the focus error signals and prevents the saturation of the focus drive circuit through the circuit 15. With setting the time constant of an LPF14 so that it answers to the frequency of the main frequency components of the focus error signals, the focus error signals are inputted to the drive coil 17 through the circuit 13.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc recording and reproducing device, and in particular, an optical disc recording and reproducing device useful when applying focus servo to an optical disc on which a pregroove is formed. It is related to.

[A essential point of the invention]

The optical disc recording and reproducing apparatus of the present invention is particularly an optical disc recording and reproducing apparatus in which a pregroove is formed.
A dead band gate circuit that can suppress signals below a predetermined level is installed in the focus servo circuit, and when the light spot crosses the track, for example during a seek operation, the traverse signal modulated by the pregroove is transmitted to the focus servo circuit. This is to prevent the focus servo from becoming erroneous due to contamination.

[Conventional technology]

FIG. 5 is a two-dimensional blow diagram showing an outline of an optical disc recording and reproducing apparatus capable of reproducing information recorded on tracks of an optical disc or recording information on an optical disc, in which 1 indicates a DC pregroove; 2 is a spindle motor, 3 is an optical head that irradiates the optical disk with laser light, and 4 is an optical disk that outputs the information of the optical disk outputted from the optical head 3 as an electric signal, or outputs a recording signal to the optical disk. The RFU path to supply, 5, is (
1. An information processing circuit that performs signal processing of raw signals or recorded signals;
6 is a signal person/output circuit.

7 is a focus servo circuit to which focus information output from the RF circuit 4 is input; 8 is a tracking servo circuit to which tracking information is also input; 9 is a thread servo circuit for controlling the feeding of the optical head 3.

10 is a system controller (CPU) of the optical disc recording/reproducing device, which outputs clock signals, timing signals, access signals, etc., and sends control signals to each circuit according to the operation mode, controlling the rotation of the spindle motor 2. It is for controlling.

The optical disc 1 is a compact disc or a read-only disc on which information is already recorded using uneven pits, such as a video disc, but a magneto-optical disc (hereinafter referred to as an MO disc) on which information can be recorded using a laser beam. ) have also been developed.

In the case of this MO disk, concentric or spiral tracks T as shown in FIG.
Pregroove G (D
C pregroove).

In the case of an MO disk, a tracking error signal is detected based on the difference between the reflected light from the pregroove G and the land portion of the track T, and tracking servo is applied so that the light spot can track the track T. Further, a focus error signal is detected by the reflected light from the land portion of the track, and focus servo is applied.

[Problem that the invention seeks to solve]

By the way, in an MO disk, for example, when the tracking servo circuit is turned off at the time of seek and the optical heald 3 is made to jump from point A1 to a desired track position A2, the optical helad 3 will jump to a high pitch modulated by this pregroove G. Reflected light consisting of frequency components is detected, and the detected signal (hereinafter referred to as a traverse signal) is mixed into the focus servo circuit 7 from the RF circuit 4 .

FIG. 7(a) is a waveform diagram showing an example of such a traverse signal St, and when such a traverse signal S+ enters the focus servo circuit 7.

This is emphasized by the high frequency phase compensation circuit of the focus servo circuit and violently shakes the objective lens up and down. When the focus servo drive circuit becomes saturated due to the high signal level, there is a problem in that the focus servo becomes erroneous due to the distorted waveform.

Furthermore, if the power supply voltage of the focus servo drive circuit is increased to prevent saturation, excessive power is supplied to the focus actuator, which may cause burnout of the focus drive coil.

[Means for solving problems]

The present invention has been made to solve this problem, and is configured so that a dead band gate circuit provided in a focus servo circuit operates when a track is sought or when tracking is turned off. .

[Effect]

This dead band gate circuit has a transfer characteristic that suppresses signals below a predetermined level of signals passing through it, and has a pass characteristic for the DC component of the signal, so it blocks most of the traverse signal. While preventing the focus error signal from being supplied to the focus actuator, it is possible to transmit a focus error signal with a low frequency component generated due to disc skew or the like. Therefore, it is possible to prevent the focus servo from entering the lock-off state due to the shadow of the traverse signal generated when tracking is turned off.

〔Example〕

FIG. 1 shows a block diagram of a focus servo system employed in the magnetic recording/reproducing apparatus of the present invention, in which 11 detects reflected light from an MO disk by an optical element FD;
A focus error detection circuit 12 for outputting a focus error signal is a preamplifier having a predetermined gain G to amplify the focus error signal to a signal of a predetermined level. Reference numeral 13 denotes a dead band gate circuit having a cutoff characteristic for a predetermined signal level, which will be described later, and is constituted by two reversely connected diodes 01.02 and a switch S consisting of an FET or the like.

14 is a low-pass filter consisting of R and C; 15 is a high-frequency phase compensation circuit for improving focus servo characteristics; 16 is a focus drive circuit; and 17 is a drive control for the focus actuator.

Note that 18 represents a control circuit that controls on/off the switch S of the dead band gate circuit 13;
Alternatively, when an HII level signal is supplied to C2 from the system controller, the switch S opens and the dead band gate circuit 13 is activated.

The transfer characteristic of the dead band gate circuit 13 during operation is such that a large attenuation amount is given to a small level signal (JeoC±O, SV) by reversely connecting the diodes Dl and D2, as shown in Fig. i2.

The focus servo system in the optical disc recording and reproducing apparatus of the present invention has the above-described configuration, and in the normal recording or reproducing mode, an "L II level signal with the tracking servo turned on is supplied to the terminal C1. In addition, since the same "L" level signal is supplied to the terminal C2 as a signal indicating the focus state, the transistors TI and T2 are both off and the switch S of the dead band gate circuit 13 is on. is controlled by.

Therefore, the focus error signal output from the focus error detection circuit 11 connected to the first main element FD passes through the preamplifier 12, the dead band gate circuit 13, the phase compensation circuit 15, and the focus drive circuit 16, and then is sent to the focus actuator. A focus servo is applied so that the light spot is focused on the disk surface.

When the tracking servo is canceled and the optical head is caused to jump, for example, the high frequency traverse signal St modulated by the pregroove of the MO disk as described above causes a focus error as shown in Fig. 3(a). It is superimposed on the signal 8f and output.

However, when this tracking servo is turned off, the terminal C+
An "H" level signal is input from the system control circuit, and the output of the differential amplifier OP is reduced and the switch S is controlled to be opened.

Then, since the dead band gate circuit 13 exhibits a transfer characteristic as shown in FIG. 2, the original focus error signal ef
The traverse signal St superimposed on
It acts to prevent the focus drive circuit from becoming saturated via the phase compensation circuit 15.

Note that by designing the low-pass filter 14 so that its time constant responds to the period of the main frequency component of the focus error signal e, a voltage corresponding to the level of the original focus error signal is set as the terminal voltage of the capacitor C. Therefore, the focus error signal caused by the eccentric skew of the disk passes through the dead band gate circuit 13 and is supplied to the drive coil 17 as a focus actuator operation signal.

When the focus servo is off for some reason, such as when starting up the device, or when the focus servo is disconnected for some reason, it is well known that the objective lens must be connected to the focus servo circuit. A search signal is supplied, and an operation to bring the camera into focus is performed.

In the embodiment of the present invention, during this focus search, the terminal C2
A “H′° level signal is supplied to the
The switch S is closed to put the dead band gate circuit 13 in the through state, and the focus servo is controlled to be in the locked state by precisely detecting the focused dX position of the three-character characteristic.

FIG. 4 shows a dead band gate circuit showing another embodiment of the present invention, in which a diode D! , D2 are formed by operational amplifiers AI, A7 and A3.

As is well known, the operational amplifiers @Z A1 and A2 constitute detection circuits with different polarities that use the offset voltages vl and v as threshold levels, and the operational amplifier A3 constitutes an adder circuit. .

In this example, the level range (eo) of the dead band signal
can be arbitrarily determined by the voltages v, , v2, so for example, the level range eQ (second
By automatically determining the traverse signal St
When this traverse signal is output, a transfer characteristic that suppresses this traverse signal can be automatically created in the focus servo circuit.

〔Effect of the invention〕

As explained above, in the optical disc recording/reproducing apparatus of the present invention, when a traverse signal modulated by the pregroove of the optical disc is mixed into the focus servo circuit, it is suppressed by the gate circuit provided with the dead zone. Since the focus servo is fixed, it is possible to prevent problems such as the focus servo coming off when tracking is turned off.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a focus servo circuit showing an embodiment of the present invention, FIG. 2 is a diagram showing transfer characteristics of a dead band gate circuit, and FIG. 3 is an example of a traverse signal mixed into a focus error signal. 4 is a circuit diagram showing another example of a dead zone gate circuit, FIG. 5 is a block diagram showing an overview of an optical disk recording/reproducing device, FIG. 6 is an explanatory diagram of a magneto-optical disk, and FIG. 7 is a circuit diagram showing another example of a dead band gate circuit. A waveform diagram of a traverse signal showing the influence of a groove is shown. In the figure, 11 is a focus error detection circuit, 12 is a preamplifier, 13 is a dead band gate circuit, 5 is a compensation circuit, 16
is the focus drive circuit, 17 is the drive coil, S
t is a traverse signal, and ef is a focus error signal.

Claims (1)

[Claims] A dead band gate circuit capable of suppressing signals below a predetermined level is provided in a focus circuit system of a device capable of reproducing or recording information on an optical disc on which a pregroove is formed, and a dead band gate circuit capable of suppressing signals below a predetermined level is provided, and a dead band gate circuit capable of suppressing signals below a predetermined level is provided. 1. An optical disc recording and reproducing apparatus, characterized in that the dead zone gate circuit prevents a traverse signal modulated by the pregroove from being supplied to a focus actuator when a light beam is traversed across a track.