JPH0495230A - Tracking controller - Google Patents

Abstract

PURPOSE:To attain the highly accurate follow-up of an optical spot to a track despite the different section shapes, etc., of the disk groups by setting previously the gain of a gain controller by a gain setting means consisting of an amplitude detection means and a preset means based on the amplitude of a groove crossing tracking error signal. CONSTITUTION:A gain controller 9 controls the gain of a tracking error signal, and a gain setting means 8 sets the gain of the controller 9. The means 8 consists of a peak value detection means 6 which detects the amplitude of a groove crossing tracking error signal and a preset means 7 which stores the value detected by the means 6 and presets the gain of the controller 9. Thus the controller 9 can control the tracking servo gain at a constant level based on a preset level despite the fluctuation of a push-pull signal caused by the different section shapes of disk groups, etc. Thus it is possible to make an optical spot follow a track with high accuracy despite the different section shapes of the disk groups.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking control device that is optimal for causing a light spot to follow a track of an optical disc or the like.

[Prior Art and Problems to be Solved by the Invention] An optical disc device includes an optical head, an access mechanism that applies a servo to move the optical head to a predetermined position on the disc, a rotation mechanism that rotates and holds the disc, an optical head and It has a control circuit for an access mechanism, a signal processing circuit for reproduction/recording signals, and a controller. The optical head includes a laser light source, a lens that focuses laser light from the laser light source, and a photodetector that detects reflected light from the disk. The control circuit of the access mechanism includes a focusing servo circuit that moves the lens vertically to control the focus of the light spot when the disk is vertically oscillated by the rotation mechanism, and a focusing servo circuit that controls the focus of the optical spot along the track. It consists of a tracking servo circuit that moves a lens in the radial direction to maintain a light spot on a track for recording and reproduction.

This tracking servo is performed based on a tracking error signal. FIG. 2 is a block diagram showing the electrical configuration of a conventional tracking control device for a previous disk.

The displacement of the light spot reflected from the rotating disk from the trunk is detected by a photodetector (3
1) and based on the output value of the photodetector (3I),
A tracking error signal is generated by a trunking error signal generation circuit (32) consisting of a current/voltage conversion circuit and a subtraction circuit. This tracking error signal corresponds to the displacement of the light spot from the track. The tracking error signal is processed by a phase compensation circuit (
33), and is applied to the switch SW1 and the drive circuit (34) for closing the tracking loop only when the negative feedback is closed. A trasokin loop control signal is supplied to the switch sw, and the drive circuit (34
) is supplied with a track-n-jump signal at the time of trunk jump. The drive circuit (34) moves the lens of the optical hent (35) in the radial direction.

An optical disk device equipped with such a tracking control device responds to either the displacement of the optical spot from the track or the tracking error signal, so it is possible to detect eccentricity due to misalignment of the disk mounting hole, resin injection and curing process. Even if there is distortion in the circumferential direction of the track that is generated during the first stage of manufacturing a disc, the optical spot can be scanned without holding it on the track.

On the other hand, the cross-sectional shape of the croup of the disk is not constant, and may be V-shaped or U-shaped, so the amount of reflected light of the optical spot and the tracking error may vary depending on the shape of the croup, such as the depth and width of the group. Signal cane or fluctuate. In this case, even though tracking servo is being performed, the output level of the tracking error signal fluctuates depending on the shape of the disk group, making it impossible to perform stable and optimal tracking. Therefore, in the tracking control device, it is impossible to make the light spot follow the track accurately, and it becomes difficult to record and reproduce information with high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tracking control device that can accurately track a light spot on a track and record and reproduce information accurately even if the groups have different cross-sectional shapes.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an optical head having a light detection means for detecting the position of a light spot with respect to a track of a disk, and an optical head based on a detection value of the light detection means. A control comprising a tracking error signal generating means for generating a tracking error signal, a phase compensating means for compensating the phase of the tracking error signal, and a driving means for moving the lens of the optical head based on the phase compensated signal. The apparatus includes a gain controller connected between the tracking error signal generating means and the phase compensating means and controlling the cane of the tracking error signal, and a cane setting means for setting the gain of the gain controller. In addition, the cane setting means includes amplitude detection means for detecting the amplitude of the groove crossing tracking error signal, and presetting means for storing the detection value detected by the amplitude detection means and presetting the gain of the cane controller. Provided is a tracking control device that performs H.

[Function] In this tracking control device, the gain of the gain controller can be preset based on the amplitude of the full-traverse tracking error signal by the gain setting means configured as the amplitude detection means and the presetting means. Usually, in an optical disk device, autofocusing servo is performed first, and then tracking servo is performed. Therefore, if the amplitude of the full-traverse tracking error signal during autofocusing servo is preset as the gain of the gain controller by the gain setting means, even if the push-pull signal changes due to the cross-sectional shape of the group, it will remain at the preset level. Based on this, the tracking servo gain can be controlled to be constant by the gain controller.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1(A) is a schematic configuration diagram of a photodetector, and FIG. 1(B) is a block diagram showing an electrical configuration of an embodiment of an optical disk device including a tracking control device of the present invention.

In order to record information on a disk or reproduce recorded information, the optical head of an optical disk device uses a photodetector (1) that detects the position of a light spot with respect to the track of the disk.
have. Note that information is usually recorded on land portions located between groups of disks or in groups within groups.

The photodetector (1) is composed of a four-part photodiode. Based on the detected values of each optical photodiode of the photodetector (1), focusing servo for controlling the focus of the light spot and tracking servo for keeping the light spot on a track are performed. Note that in this example,
The focusing servo uses an error signal detected by the astigmatism method, and the tracking servo uses an error signal detected by the push-pull method. That is, as shown in FIG. 1(A) (13), the current It, 12.13 and I4 output by each photodiode depending on the position of the light spot on the photodetector (1)
is input to a focusing error signal generation circuit (2) and a tracking error signal generation circuit (5). A focusing error signal generation circuit (2) and a tracking error signal generation circuit (5) are connected to the photodetector (1).
It consists of a current/voltage conversion circuit that converts the output currents It, 12.13, and I4 of the four photodiodes into voltages, and a subtraction circuit that subtracts the respective converted voltage values to generate an error signal. There is. The focusing error signal generation circuit (2) uses a subtraction circuit to
A focusing error signal 1F -(11+13>-(I2+14)) is generated, and a tracking error signal generating circuit (5) generates a tracking error signal It-, (Ii+12)-(13+14) using a subtraction circuit.

The focusing error signal If generated by the focusing error signal generating circuit (2) is transmitted to the optical head (1).
In order to prevent oscillation due to phase lag in step 3), the signal is input to the phase compensation circuit (3). The phase-compensated focusing error signal is supplied to the switch SWl, and the driving circuit (
4), the lens (13a) of the optical head (13) is moved to perform focus servo. Further, when performing focus detection, the switch SWI is turned off and a pickup up/down signal for moving the lens (13a) up and down is supplied to the drive circuit (4). Lens (1)
3a) Detect the focal point position when passing through the focal point with the vertical movement.

The switch SWI is ONL in response to this automatic focus detection signal, and thereafter focus servo is performed based on the detected focus position.

On the other hand, in the tracking servo, the tracking error signal It generated by the tracking error signal generation circuit (5) is supplied to the gain control circuit (9). The output level of the gain control circuit (9) that controls the gain of the tracking error signal (2) is preset based on the tracking error signal It during the focus servo.More specifically, the output level of the gain control circuit (9) that controls the gain of the tracking error signal The cross-groove tracking error signal It generated by the generation circuit (5) is supplied to a gain setting circuit S). This gain setting circuit (8) has a peak value detection circuit (6) to which the groove crossing tracking error signal It is supplied. The peak value detection circuit (6) outputs the peak value amplitude of the tracking error signal It, which varies depending on the cross-sectional shape of the disk group, and sends it to the latch circuit q) of the gain setting circuit (8) as a preset amount. Stored. Then, based on the preset amount stored in the latch circuit σ), the gain control circuit (9) controls the output level of the tracking error signal It to be substantially constant.

Therefore, the tracking error signal output from the gain control circuit (9) does not include servo cane fluctuation components caused by the cross-sectional shape of the croup of the disk.

The tracking error signal controlled by the gain control circuit (9) is supplied to the phase compensation circuit (10). This phase compensation circuit (10) prevents oscillation due to phase delay of the tracking error signal.

The tracking error signal whose phase has been compensated by the phase compensation circuit (10) is sent to the drive circuit (
11), and this drive circuit (11) moves the lens (13a) of the optical head (13) in the radial direction.

Further, a track jump signal is given as a pulse to the drive circuit (11).

As described above, the drive circuit (11) responds to the tracking error signal by adjusting the lens (13a) of the optical head (13).
) to keep the light spot on track. In this case, in order to accurately follow the light spot along the track, the lens (13) of the optical head (13) is
The amount of radial movement in a) is small and has a limit. Therefore, the tracking error signal is also applied to the switch SW3 through the switch SW2, and is applied to the drive circuit (12) through this switch SW3. This drive circuit (12) is connected to the lens (13) of the optical belly button (+3).
When the amount of movement in a) reaches the limit, the entire optical head (13) is moved in response to the tracking error signal, and the lens (13a) is controlled to be located at the center of the movable range.

Furthermore, when searching, the tracking servo system is
F, a run-al feed signal is supplied to the switch SW3, and the drive circuit (12) outputs the optical head (+3).
Move the whole thing. This radial sending signal is supplied from the destination disk controller based on the current position of the optical spot and the address data of the disk. The switch SW3 is closed based on the radial sending signal, and the optical head (13) is moved approximately to the vicinity of the designated address by the drive circuit (I2). Further, based on the position of the light spot after the movement and the number of excess or insufficient tracks, the jump pink signal is given to the drive circuit (11) of the tracking servo system, and the light spot is moved to a predetermined track by jumping.

In such a tracking control MW, the groove crossing tracking error signal It when only the focus servo is ON is supplied to the peak value detection circuit (6) of the gain setting circuit (8), and then sent to the latch circuit (7). The stored preset amount can be supplied to the gain control circuit (9) as a control signal. Therefore, even if the level of the tracking error signal (t) varies due to the cross-sectional shape of the disk group, the output level to the drive circuit (11) can be set to be substantially constant. In addition, the optical spot can follow the track of the disc with high precision, and information can be recorded and reproduced with high precision.

In the above embodiment, the peak value detection circuit (6) and the gain control circuit have been described as having analog configurations, but they may also be configured as digital circuits. Further, as the presetting means, a random access memory (RAM) may be used instead of the latch circuit (7).

Further, in the above embodiment, the tracking servo is performed by a push-pull method, but the positional shift of the light spot from the trunk may be performed by a three-beam method, a wobbling method, a heterodyne method, or the like. In addition, the auto-force sink sabot uses conventional methods such as the critical angle method, the Foucault method, and the Naifetsu method, which are limited to the astigmatism method.
can be done.

[Effects of the Invention] The tracking control device of the present invention can cause a light spot to follow a track with high precision even if the cross-sectional shapes of the groups of discs are different, and can record and reproduce information with high precision.

[Brief explanation of drawings]

Figure 1 (^) is a schematic configuration diagram of the photodetector, Figure 1 (+3>
2 is a block diagram showing the electrical configuration of an embodiment of an optical disk device including the tracking control device of the present invention, and FIG. 2 is a block diagram showing the electrical configuration of a conventional tracking control device. (1)...photodetector,

Claims (1)

[Claims] an optical head having a light detection means for detecting the position of a light spot with respect to a track of a disk; a tracking error signal generation means for generating a tracking error signal based on a detection value of the light detection means; A control device having a phase compensation means for compensating, and a drive means for moving the lens of the optical head based on the phase compensated signal, the control device being connected between the tracking error signal generation means and the phase compensation means. and a gain controller for controlling the gain of the tracking error signal, and a gain setting means for setting the gain of the gain controller,
A tracking control device in which the gain setting means includes an amplitude detection means for detecting the amplitude of a groove crossing tracking error signal, and a presetting means for storing a detection value detected by the amplitude detection means and presetting a gain of a gain controller. .