JPH01276437A - Disk device - Google Patents

Abstract

PURPOSE:To execute stable tracking by decreasing an amplifying to a track difference signal when the amplitude of a high frequency component is generated in the signal by a defect in a recording track. CONSTITUTION:A light beam irradiates an optical disk and a track difference signal V0 of the recording track, which is generated by the photo-electric converting output of an optical system, is supplied to a phase advance compensating circuit 41. Then, a track difference signal V1, whose phase is advanced, is supplied to a phase delay compensating circuit 42. For the compensating circuit 42, diodes (D)1 and D2 are cut off at the time of normal tracking and a signal V3 to correspond to an input voltage is made equal to with the signal V1, amplified by an amplifier 42a and supplied to a driving circuit 43. When a noise is generated by the defect of the optical disk, the D1 or D2 is conducted and the high frequency gain is decreased. Thus, the stable tracking can be executed even to the defect of the optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a disc device for recording or reproducing information on, for example, an optical disc.

(Prior Art) As is well known, various disc devices have been developed that record information on an optical disc or read information recorded on an optical disc using, for example, a laser beam output from a semiconductor laser.

In such optical disk devices, access speeds and transfer speeds have been increased, and the number of rotations of the optical disks has inevitably increased. Therefore, in such a device, recording and playback are stabilized by increasing the tracking servo gain (amplifier gain for the dock difference signal) to compensate for the eccentricity of the optical disk, and widening the tracking servo band. The aim is to improve the ability to get into the truck and make the access operation safer.

However, in the optical disk device mentioned above, the gain of the tracking servo loop is increased and the band is widened.
If there is a defect in the track, there is a drawback that the recording medium may deviate from the track during recording or reproduction in response to a track control signal generated from the defect.

Therefore, there is a drawback that stable tracking cannot be performed for defects in the optical disc.

(Issue 8 to be solved by the invention) This invention eliminates the drawback of not being able to perform stable tracking with respect to defects in the disc. The purpose is to provide a disk device that can.

[Structure of the Invention] (Means for Solving the Problems) A disk device of the present invention includes an optical system that detects and photoelectrically converts light obtained by irradiating light onto a disk having a recording track, and a Generating means for generating and amplifying a track difference signal for the recording track using a photoelectric conversion output, detecting the amplitude of a high frequency component of the track difference signal from this generating means, and changing the gain to lower the gain of the amplification in response to this detection. and means for causing the optical system to follow the recording track of the disk using a signal from the generating means amplified by the gain of the gain changing means or a signal from the generating means amplified by the gain of the continuous line. It is configured.

(Function) When this invention detects that the amplitude of a high frequency component has occurred in the track difference signal due to a defect in the recording track, the optical system lowers the amplification gain for that signal, and the optical system
This prevents the player from straying from the track being played.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 shows a disk device. A spiral or concentric groove (track) is formed on the surface of an optical disk (disc) 1, and the optical disk 1 is rotated by a motor 2 at a constant speed, for example. This motor 2 is controlled by a motor control circuit 18.

As shown in FIG. 3, the optical disc 1 has a donut-shaped metal coating layer, ie, a recording film made of tellurium or bismuth, coated on the surface of a circular substrate made of glass or plastic, for example. A notch, that is, a reference position mark 1□, is provided near the center of the metal coating layer.

Further, on the optical disk 1, as shown in FIG. 3, reference position marks 1. It is divided into 256 sectors from 0 to 255, with 0 as 0. On the optical disk 1, variable length information is recorded over multiple blocks, and on the optical disk 1, 3 blocks are recorded in 36,000 tracks.
00,000 blocks are now formed.

The number of sectors in one block on the optical disc 1 is, for example, 40 sectors on the inner side and 20 sectors on the outer side. At the start position of the block, a block header A consisting of a block number, track number, etc. is recorded, for example, when the optical disc 1 is manufactured.

Furthermore, if each block on the optical disc 1 does not end at the sector switching position, a block gap is provided so that each block always starts from the sector switching position.

Recording and reproduction of information on the optical disc 1 is performed by an optical head 3, as shown in FIG. This optical head 3 is fixed to a drive coil 13 that constitutes a movable part of a linear motor, and this drive coil 13 is connected to a linear motor control circuit 17.

A linear motor position detector 26 is connected to this linear motor control circuit 17, and this linear motor position detector 26 is connected to an optical scale 2 provided on the optical head 3.
5, a position signal is output.

Further, a permanent magnet (not shown) is provided in the fixed part of the linear motor, and when the drive coil 13 is excited by the linear motor control circuit 17, the optical head 3 is moved in the radial direction of the optical disk 1. It has become so.

An objective lens 6 is held on the optical head 3 by a wire or a leaf spring (not shown), and the objective lens 6 is moved in the focusing direction (
The driving coil 4 allows movement in the tracking direction (direction perpendicular to the optical axis of the lens).

Further, the laser beam generated by the semiconductor laser 9 driven by the laser control circuit 14 is transmitted to the collimator lens 1.
1a1 half prism 11b1 is irradiated onto the optical disk 1 through the objective lens 6, and the reflected light from the optical disk 1 is transmitted to the photodetector 8 via the objective lens 6, the half prism 11b1, the condensing lens 10a1, and the cylindrical lens 10b. be guided.

This photodetector 8 has four divided photodetection cells 8a%8b
It is composed of s 8c and 8d.

Note that the above-mentioned wire-based objective lens driving device is described in Japanese Patent Application No. 61-284591.
The explanation thereof will be omitted here.

The output signal of the photodetection cell 8a of the photodetector 8 is supplied to one end of the adder 3Qa, 30c via the amplifier 12a, and the output signal of the photodetection cell 8b is supplied to the adder 30b, 30d via the amplifier 12b. is supplied to one end of the photodetection cell 8
The output signal of c is passed through an amplifier 12c to an adder 30b,
The output signal of the photodetecting cell 8d is supplied to the other end of the adders 30a and 30d via an amplifier 12d.

The output signal of the adder 30a is supplied to the inverting input terminal of the differential amplifier OP1, and the output signal of the adder 30b is supplied to the non-inverting input terminal of the differential amplifier OPI. As a result, the differential amplifier OPI operates as the adder 30a, 30.
A track difference signal is supplied to the tracking control circuit 16 according to the difference in b. This tracking control circuit 16 creates a track drive signal according to the track difference signal supplied from OPl.

A track drive signal output from the tracking control circuit 16 is supplied to the drive coil 4 in the tracking direction. Further, the track difference signal used in the tracking control circuit 16 is supplied to the linear motor control circuit 17.

Further, the output signal of the adder 30c is transmitted to the differential amplifier OP2.
The output signal of the adder 30d is supplied to the non-inverting input terminal of the differential amplifier OP2. As a result, the differential amplifier OP2 is connected to the adder 30c.
, 30d, a signal regarding the focus point is supplied to the focusing control circuit 15.

The output signal of the focusing control circuit 15 is supplied to the focusing drive coil 5, and is controlled so that the laser beam is always in just focus on the optical disk 1.

When focusing and tracking are performed as described above, the sum signal of the outputs of each of the photodetection cells 8a to 8d of the photodetector 8, that is, the output signal from the adder 30a130b, is the pit ( The unevenness of recorded information) is reflected.

This signal is supplied to the video circuit 19, and the video circuit 1
At step 9, image information and address information (track number, sector number, etc.) are reproduced.

The tracking control circuit 16 also controls the CPU 2.
The objective lens 6 is moved in response to a track jump signal supplied from the D/A converter 22 from the D/A converter 22, and the beam light is moved by one track.

The laser control circuit 14 and the focusing control circuit 15
, tracking control circuit 16, linear motor control circuit 1
7. The motor control circuit 18, video circuit 19, etc. are controlled by a CPU 23 via a pass line 20, and this CPU 23 is configured to perform predetermined operations according to a program stored in a memory 24. There is.

Further, the D/A converter 22 is used to exchange information between the focusing control circuit 15, the tracking control circuit 16, the linear motor control circuit 17, and the CPU 23, respectively.

As shown in FIG. 1, the tracking control circuit 16 includes a switch 40. It is composed of a phase lead compensation circuit 41, a phase lag compensation circuit 42, and a drive circuit 43.

The switch 40 turns the tracking servo on and off by turning it on and off in response to a control signal from the CPU 23.

The phase lead compensation circuit 41 is a well-known circuit that compensates for the phase lead of the track difference signal VO supplied from the OP1.

The phase lag compensation circuit 42 includes the phase lead compensation circuit 4.
1, and is composed of, for example, resistors R1, R2, R3, a capacitor C1, a switch S1, diodes D1, D2, and an amplifier 42a.

The track difference signal (track tracking signal) supplied from the phase lead compensation circuit 41 is the signal v1, and the signal 2 corresponding to the voltage across the capacitor C is the signal v1.
The signal is delayed by a time constant "τ-C(R1+R2)J" set by the capacitor C and resistors R1 and R2.

When the above switch S1 is closed, the signal ■1 is turned on (
When the voltage is changing, the signal v2 moves almost equally to the signal V1, so both capacitors D1 and D2 are cut off, and the signal v corresponding to the input voltage of the amplifier 42a is cut off.
3 (track control signal) is approximately equal to (lags in phase) the signal V1.

However, if noise due to a defect occurs in the signal v1 as shown in FIG. 5(a), the signal V2 cannot respond to this noise, so the noise tends to occur in the signal v3. However, at this time, either diode D1 or D2 becomes conductive, so if the resistor R3 is set to a smaller value than the resistor R2, the noise will be cut from the signal V3 and will not be transmitted to the track drive signal. There is no such thing.

Therefore, the loop characteristics of the tracking servo loop are as shown by the solid line in the normal tracking state, and as shown by the broken line when either diode D1 or D2 is in the conductive state (when the limiter is activated). It is shown as follows.

The switch S1 is turned on and off in response to a control signal from the CPO 23, so that it is turned off when tracking is started, as shown in FIG. , is set to be turned on. As a result, as shown in FIG. 3(d), a signal with a high frequency component is generated to drive the objective lens 6 to the target track, and it is also stable against defects in the optical disc 1. tracking operations can be performed.

Next, the access operation in such a configuration will be explained. For example, a block number to be accessed is supplied to the CPU 23 from an external device (not shown). Then, the CPU 23 uses the block number to calculate the track number and start sector number to be accessed using a table (not shown). Then, the CPU 23 determines the current position based on the track number and sector number (the contents of the block header A of the track to which the beam light from the optical head 3 currently corresponds) as address information supplied from the video circuit 19. At this time, the optical head 3, that is, the track that the beam light corresponds to, is the target track (
(movement position), the access ends.

Further, if there is a difference between the track corresponding to the optical head 3 and the target track, the CPU 23 calculates the difference (track difference) between the target track and the current track and the direction (inside, outside). Based on the result of this calculation, CPU2
B determines whether the distance to be moved is long distance (more than 50 tracks) or short distance. If the result of this judgment is a long distance, coarse access is performed, and if the result is a short distance, fine access is performed.

After the precise access, information is recorded, reproduced, etc. on the accessed track.

In such a state, the tracking operation will be described as shown in FIGS. 6(a) to 6(d). First, when moving by the access operation, the switch 40 and Sl are turned off (opened) so that the tracking servo is not applied. When the vehicle enters the tracking mode, the switch 40 is turned on and closed), and the switch S1 remains off.

That is, the signals from adders 30a and 30b are supplied to differential amplifier OPI. Then, the differential amplifier OPI outputs the track difference signal VO obtained from the photodetector 8 (see FIG. 6).
a)) is set to switch 4 in the tracking control circuit 16.
0 to the phase lead compensation circuit 41. As a result, the phase lead compensation circuit 41 outputs the track difference signal V1, which is obtained by leading the phase of the supplied track difference signal VO, to the phase lag compensation circuit 42.

In this phase lag compensation circuit 42, since the switch S1 is off, the capacitors p1 and D2 do not work, and the signal v3 corresponding to the input voltage of the amplifier 42a is approximately equal to the signal v1 (the phase is delayed). ing.

Therefore, when getting into the destination truck, as shown in Figure 6 (d)
), a high frequency component with a high amplitude is generated, and the objective lens 6 can be driven.

Thereafter, when the driver gets into the target truck and the tracking becomes stable after a predetermined period of time has elapsed, the CPU 23 turns on (closes) the switch S1.

Thereby, stable tracking operation can be performed even with respect to defects in the optical disc 1.

That is, the signals from adders 30a and 30b are supplied to differential amplifier OPI. Then, the differential amplifier OPI outputs the track difference signal vO obtained from the photodetector 8 to the phase lead compensation circuit 41 via the switch 40 in the tracking control circuit 16.

As a result, the phase lead compensation circuit 41 outputs the track difference signal V1, which is obtained by leading the phase of the supplied track difference signal vO, to the phase lag compensation circuit 42.

During normal tracking, this phase lag compensation circuit 42
In other words, when the track difference signal v1 to be supplied is changing slowly, the signal v2 moves almost equally to the signal v1, so both capacitors D1 and D2 are cut off.
The signal v3 corresponding to the input voltage of the amplifier 42a is approximately equal to the signal v1 (the phase is delayed).

As a result, a signal obtained by amplifying this signal v3 by the amplifier 42a is output to the drive circuit 43 as a track drive signal.

Then, the drive circuit 43 supplies a predetermined current to the coil 23 according to the supplied track drive signal, and the objective lens 6
is driven in the horizontal direction to perform tracking correction.

Furthermore, if noise due to a defect occurs in the signal v1 as shown in FIG. 5(a), the signal v2 cannot respond to this noise, so the noise tends to occur in the signal v3. However, at this time, either the diode D1 or D2 becomes conductive, so that the noise in the signal v3 is cut off and is not transmitted to the track drive signal, as shown in FIG. 4(b).

As described above, the high frequency component of the track control signal is detected due to a defect in the optical disc 1, and when this detection is performed, the gain of the tracking servo loop in the high frequency range is lowered. Thereby, when the rotational speed of the optical disc is increased, stable tracking can be performed even with respect to defects in the optical disc.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a disk device that can perform stable tracking even with respect to defects in the disk.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 shows a schematic configuration of a tracking control circuit, FIG. 2 shows a configuration of a disk device, and FIG. 3 shows a configuration of an optical disk. Fig. 4 is a characteristic diagram to explain the relationship between the gain and frequency of the tracking servo lube, Fig. 5 is a signal waveform diagram showing signal waveforms of each part in the phase lag compensation circuit, and Fig. 6 is a signal waveform diagram of important parts in operation. FIG. 3 is a diagram for explaining waveforms and switching timing of switches. 1... Optical disk, 3... Optical head, 4.5...
・Coil, 6... Objective lens, 8... Photodetector, 9
... Semiconductor laser, OPI... Differential amplifier, 16.
...Tracking control circuit, 23...CPU. 40, Sl switch, 41... phase lead compensation circuit, 4
2... Phase lag compensation circuit, 42a... Amplifier, R1
, R2, R3...Resistor, C...Capacitor, Dl,
D2...diode. Applicant's agent Patent attorney Takehiko Suzue Figure 3

Claims (1)

[Claims] An optical system that detects and photoelectrically converts light obtained by irradiating light onto a disk having a recording track, and generates a track difference signal with respect to the recording track by the photoelectric conversion output of this optical system. , a generating means for amplifying the signal, a gain changing means for detecting the amplitude of the high frequency component of the track difference signal from the generating means, and lowering the gain of the amplification in response to this detection; A disc device comprising: means for causing the optical system to follow a recording track of the disc using a signal from the generating means or a signal from the generating means amplified with a normal gain.