JPH03173938A - Tracking servo device - Google Patents

Abstract

PURPOSE:To realize stable jumping by generating a brake pulse with a pulse width or an amplitude in response to an elapsed time for a period when a kick pulse is applied and applying the pulse to a tracking actuator. CONSTITUTION:A pulse width detection circuit 15 measures an elapsed time for the application period of a kick pulse, a brake pulse with a pulse width or an amplitude generated by a brake pulse generating circuit 12 in response to the measured time is applied to a tracking actuator 9 and a brake torque in response to the pulse width of the kick pulse is delivered to the tracking actuator 9. The brake torque in response to the pulse width of the kick pulse is delivered to the tracking actuator in this way to realize always stable jumping even to a disk with a different track pitch with simple circuit constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a tracking servo device in an information recording disk performance device.

BACKGROUND ART A performance device for an information recording disk (hereinafter simply referred to as a disk) such as a video disk or a digital audio disk requires a pickup spot for reading recorded information to always accurately follow the recording track regardless of the eccentricity of the disk. A tracking servo device is essential for precise control.

This tracking servo device generates a tracking error signal according to the amount of deviation of a recording information reading spot in the disc radial direction with respect to a recording track of the disc, and adjusts the recorded information reading spot in the disc radial direction according to the tracking error signal. This is a so-called closed servo control system in which the position of the recording track is controlled by driving a tracking actuator to bias the recording track.

In addition, in such a servo device, during a so-called jump operation in which the recorded information reading spot jumps over the recording track, the servo loop is placed in an oven (open) state and a kick pulse with a polarity corresponding to the jump direction is applied to the tracking actuator. At the zero-crossing timing of the tracking error signal during operation, a brake pulse with the opposite polarity to the kick pulse is applied to the actuator for a certain period of time to apply a certain braking force, and then the servo loop is closed and the servo is activated. Control is performed to perform the retraction.

By the way, although the pitch of the recording tracks of a disc (hereinafter simply referred to as track pitch) is determined as a standard, there may be discs with track pitches that are different from the specified pitch. For example, there is a case where a disk with a small track pitch is standardized to improve recording density. When performing a track jump on such a disc, the braking force required when retracting the servo differs depending on the track pitch, so applying a constant braking force to the actuator as described above will cause the track pitch to change. If the pitch is larger than the specified pitch, the braking force will be insufficient, and if it is smaller than the specified pitch, the braking force will be excessive, making it impossible to perform a stable track jump.

Conventionally, the following devices are known as devices that make the braking force variable in order to solve this problem. In other words, ■ Detect the slope of the tracking error signal near the zero cross, and adjust the brake pulse application time (
(Pulse Width)
(see publication).

■ A device that applies a brake pulse during the period until the tracking error signal level reaches a predetermined level after detecting the peak point (see Japanese Patent Laid-Open No. 83-140428)
.

■ A device that applies a brake pulse during the period up to the detection of the peak point of the tracking error signal (Japanese Patent Laid-Open No. 63-
(See Publication No. 129574).

■ A device that measures the time from the zero cross point of the tracking error signal to the detection of the peak point and controls the application time of the brake pulse according to this measured time (Japanese Patent Laid-Open No. 63-12
(See Publication No. 9578).

(2) A device that applies a brake pulse until a certain period of time has elapsed after detecting the peak point of the tracking error signal (see Japanese Patent Laid-Open No. 129572/1983).

However, the device described in (1) requires a tilt detection circuit, which has the disadvantage of complicating the circuit configuration.
The devices from (1) to (2) are all configured to detect the peak point of the tracking error signal after a zero cross, so a peak detection circuit is required, which complicates the circuit configuration and reduces noise. There were problems such as instability due to this and errors due to level fluctuations.

SUMMARY OF THE INVENTION [Object of the Invention] Therefore, an object of the present invention is to provide a tracking servo device that can always realize stable jump operation even for disks with different track pitches with a simple circuit configuration.

[Structure of the Invention] A tracking servo device according to the present invention includes means for generating a tracking error signal in accordance with the amount of deviation in the disk radial direction of a recorded information reading spot with respect to a recording track of a disk, and A tracking servo device including a servo loop that has a driving means for biasing the recorded information reading spot in the disk radial direction, and that enters an oven state in response to a jump start command and enters a closed state upon completion of a jump operation, a detection means for detecting that the recorded information reading spot has arrived at an intermediate position between adjacent recording tracks based on the tracking error signal during a jump operation; and a detection point by the detection means from the time of the jump start command. a kick pulse applying means for generating a kick pulse of a predetermined amplitude and applying it to the driving means during a period of time; a measuring means for measuring elapsed time during the application period of the kick pulse; and a brake pulse applying means for generating a brake pulse having a pulse width or amplitude and applying the generated brake pulse to the driving means at the time when the kick pulse disappears.

[Operation of the invention] The tracking servo device according to the invention measures the elapsed time during the kick pulse application period, generates a brake pulse with a pulse width or amplitude according to this measured time, and applies it to the tracking actuator. , applies a braking force to the tracking actuator according to the pulse width of the kick pulse.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, there are three beam spots obtained by converging the laser beam, namely a spot S1 for reading recorded information and this spot S! A pair of tracking information detection spots s2. which precede and follow, respectively, move relative to the disk in the rotational direction. s3 is irradiated onto the recording track T of the disk from a pickup (not shown) with the positional relationship shown.

Light reflected from the disk surface by these beam spots enters photoelectric conversion elements 1, 2, and 3 built into the pickup.

The photoelectric conversion element 1 consists of a so-called four-part photodetector, and the sum of the four outputs becomes a read RF (high frequency) signal. On the other hand, each output of the pair of photoelectric conversion elements 2 and 3 is supplied to a differential amplifier 4 to derive a difference in re-output, and this difference output (S2-
S3) becomes the tracking error signal. Due to the jumping motion, each beam spot 81 to S3 is moved to the position shown in FIG. 2(A).
As shown in the figure, when moving from one recording track T1 to the adjacent recording track T2, a tracking error signal (S
2-S3) has a sinusoidal waveform as shown in FIG. position and adjacent track T,
, T2, respectively.

The tracking error signal is supplied to a loop switch 6 after its frequency and phase characteristics are compensated by an equalizer 5 . The tracking error signal that has passed through the loop switch 6 is sent to the adder 7.
and tracking actuator 9 via drive circuit 8
is supplied to This tracking actuator 9 is
In order to cause the recording) 11 information reading spot hs+ to accurately follow the recording track T, the spot S1 is biased in the disk radial direction according to the tracking error signal level. Through the above steps, a tracking servo loop is formed.

On (close)/off (open) control of the loop switch 6 is performed by a jump control sequence circuit 10. When the loop switch 6 is in the on state, the tracking servo loop is in a closed state, and in this loop closed state, tracking servo is performed according to the tracking error signal level. The jump control sequence circuit 10 turns off the loop switch 6 in response to the jump command. In the loop oven state in which the loop switch 6 is in the OFF state, the kick pulse generated by the kick pulse generation circuit 11 and the play and kibalus generated by the brake pulse generation circuit 12 are added to the adder 13.
A jump operation is performed by applying the signal to the tracking actuator 9 via the drive circuit 7 and the drive circuit 8.

In order to set the timing for the disappearance of the kick pulse and the generation of the brake pulse during the jump operation, it is detected that the recorded information reading spot S1 has arrived at the intermediate position between adjacent recording tracks, that is, the zero cross point of the tracking error signal. A zero cross detection circuit 14 is provided. This zero cross detection circuit 14 is composed of, for example, a well-known zero cross comparator, and provides a trigger to the kick pulse generation circuit 11 at the detection timing. The kick pulse generation circuit 11 responds to a jump start command from the jump control sequence circuit 10 to determine the jump direction (FWD/RE).
It is configured to generate a kick pulse having a polarity and a predetermined amplitude according to V), and to stop generating the kick pulse at the detection timing of the zero cross detection circuit 14. In other words, the Ki-Tsuku Pulse starts from the time of the jump start command.
This occurs during the period before the zero loss detection point of the soaking error signal.

The application period of this kick pulse, that is, the pulse width of the kick pulse is detected by a pulse width detection circuit 15.

A specific example of the circuit configuration of this pulse width detection circuit 15 will be described later. The detected pulse width information by the pulse width detection circuit 15 is also supplied to the brake pulse generation circuit 12. The brake pulse generation circuit 12 generates a brake pulse having a polarity opposite to that of the kick pulse and a predetermined amplitude at the time when the kick pulse disappears, and assigns the time when the pulse disappears to the pulse width information detected by the pulse width detection circuit 15. Set. That is, the brake pulse is generated at the time when the kick pulse disappears, and its pulse width is determined according to the pulse width of the kick pulse. In other words, the pulse width of the brake pulse is determined according to the track pitch of the recording track.

Next, a specific example of the circuit configuration of the pulse width detection circuit 15 will be described.

FIG. 3 is a block diagram showing an example in which the pulse width detection circuit 15 has a digital circuit configuration.

Basically, it consists of an up/down counter 21, into which preset data set by a preset data setting circuit 22 is loaded in response to a load signal generated before application of a kick pulse. Ru. For example, if you want to make the pulse width of the brake pulse the same as that of the kick pulse, use the preset data "0".
' will be loaded. The up/down counter 21 is in an up-counting state when a kick pulse is applied, and is in a down-counting state when no kick pulse is applied, and counts up or down a clock whose cycle is sufficiently smaller than the pulse width of the kick pulse.

The circuit operation of the pulse width detection circuit 15 having such a digital circuit configuration will be explained with reference to the timing chart of FIG.

When a jump start command pulse (a) is generated from the jump control sequence circuit 10, the up/down counter 21 loads preset data using this jump start command pulse (a) as a load signal. Further, a kick pulse (b) is generated from the kick pulse generation circuit 11 in response to the falling edge of the jump start command pulse (a). Upon generation of this kick pulse (b), the up/down counter 21 starts counting up, and stops counting when the kick pulse (b) disappears.

The pulse width of the kick pulse (b) is expressed by the count value (C) of the up/down counter 21 and the period of the clock.

At the time when the kick pulse (b) disappears, the brake pulse generation circuit 12 generates a brake pulse (d), and at the same time, the up/down counter 21 starts counting down. Then, the up/down counter 21 stops counting operation and outputs a stop signal (e) when the count value (c) reaches rOJ. This stop signal (
In response to e), the brake pulse generation circuit 12 stops generating the brake pulse (d).

By the above operation, a brake pulse (d) having a pulse width equal to that of the kick pulse (b) is generated. Note that it is not necessary to set the pulse width of the brake pulse (d) equal to the pulse width of the kick pulse (b).
It can be arbitrarily set by changing the value of preset data.

FIG. 5 is a block diagram showing an emergency example in which the pulse width detection circuit 15 has an analog circuit configuration.

The pulse width detection circuit 15 in this example includes a sawtooth wave generation circuit 23 that generates a sawtooth wave with a predetermined slope, and a sample hold (S/ H) a circuit 24;
It consists of this sample hold circuit 24 and a comparator 25 that compares the sawtooth wave. As the sawtooth wave generating circuit 23, one having a well-known circuit configuration as shown in FIG. 6 may be used.

The circuit operation of the pulse width detection circuit 15 having such an analog circuit configuration will be explained with reference to the timing chart of FIG.

A reset pulse (d) is generated in response to the jump start command pulse (a), and the sawtooth wave generation circuit 23 is reset by this reset pulse (d), and at the falling edge of the jump start command pulse (a). In response, the kick pulse generation circuit 11 generates a kick pulse (b). Then, a sample hold pulse (e) and a brake pulse (f) are generated in synchronization with the falling edge of the kick pulse (b). At this time, the sample and hold circuit 24 samples and holds the level of the sawtooth wave (C) in response to the sample and hold pulse (e). A reset pulse (d) is generated in synchronization with the falling edge of the sample hold pulse (e), and this reset pulse (d)
The sawtooth wave generating circuit 23 is reset again.

Then, when the level of the sawtooth wave (C) reaches the hold level of the sample and hold circuit 24, the comparator 2
5 outputs a stop signal (g), and this stop signal (
Brake pulse ([) in response to the rising edge of g)
disappears.

In addition, in the above embodiment, the case where the pulse width of the brake pulse is set according to the pulse width of the kick pulse is explained, but in short, it is sufficient to set the brake force according to the pulse width of the kick pulse. Therefore, the same effect can be obtained by setting the amplitude of the brake pulse according to the pulse width of the kick pulse. in this case,
For example, in the pulse width detection circuit 15 shown in FIG. 5, the hold level of the sample and hold circuit 24 may be set as the amplitude of the brake pulse.

As described in detail, the tracking servo device according to the present invention measures the elapsed time during the kick pulse application period, generates a brake pulse with a pulse width or amplitude according to the measured time, and applies the brake pulse to the tracking actuator. By applying tMiffl, a braking force corresponding to the pulse width of the kick pulse is applied to the tracking actuator, so it is possible to always achieve stable jump operation even for discs with different track pitches with a simple circuit configuration. Become.

Furthermore, even if the sensitivity of the tracking actuator and the gain of its drive circuit differ from one disk performance device to another, it is possible to cope with jump operations without the need for adjustment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the moving position of a recorded information reading spot with respect to a recording track and a tracking error signal, and FIG. 3 is a diagram showing the pulse in FIG. 1. 4 is a block diagram showing an example of the width detection circuit, FIG. 4 is a timing chart for explaining the circuit operation of FIG. 3, and FIG. 5 is a block diagram showing another example of the pulse width detection circuit in FIG. FIG. 6 is a circuit diagram showing an example of a specific circuit configuration of the sawtooth wave generating circuit shown in FIG. 5, and FIG. 7 is a timing chart for explaining the operation of the circuit shown in FIG. Explanation of symbols of main parts 1 to 3...Photoelectric conversion element 6...Loop switch 9...Tracking actuator 10...
... Jump control sequence circuit 11 ... Kick pulse generation circuit 12 ... Brake pulse generation circuit 14 ... Zero cross detection circuit 15 ... Pulse width detection Circuit Figure 3 Figure 5 Figure 6 Figure 4 Figure 7

Claims (1)

[Scope of Claims] Means for generating a tracking error signal in accordance with the amount of deviation in the disc radial direction of a recorded information reading spot with respect to a recording track of an information recording disc, and a means for generating a tracking error signal in accordance with the deviation amount in the disc radial direction of the recorded information reading spot with respect to a recording track of an information recording disc; and a drive means for biasing the disk in the radial direction,
A tracking servo device including a servo loop that enters an open state in response to a jump start command and becomes a closed state upon completion of a jump operation, wherein the recorded information reading spots are adjacent to each other based on the tracking error signal during the jump operation. a detection means for detecting arrival at an intermediate position between recording tracks; and a kick pulse for generating a kick pulse of a predetermined amplitude and applying it to the drive means during a period from the time of the jump start command to the time of detection by the detection means. pulse applying means; measuring means for measuring the elapsed time during the application period of the kick pulse; generating a brake pulse with a pulse width or amplitude according to the time measured by the measuring means, and applying the brake pulse at the time when the kick pulse disappears; A tracking servo device comprising: brake pulse applying means for applying a brake pulse to the driving means.