JPH0227529A - Tracking servo device - Google Patents

Abstract

PURPOSE:To accelerate the track jump of an optical disk drive by detecting a pull-in point by monitoring a tracking error signal, finding the number of times of zero-cross, and turning on tracking servo at the pull-in point, and driving and moving a slide motor. CONSTITUTION:The slide motor 9 is driven by data from a CPU1 supplied via a D/A converter 2 via a power amplifier 8. And the position of the slide motor 9 is detected by counting a pulse from a slide encoder 10 by a counter circuit 12, and a tacking actuator 5 is driven, then, a head is moved on a disk. also, the tracking error signal is monitored by an A/D converter 7, and when the error signal zero-crosses, a switch 15 is turned on, then, a tracking servo operation is performed. At this time, only the low frequency component of the error signal is detected by the CPU1, and correction is performed by driving the slide motor 9 via the D/A converter 2. In such a way, it is possible to perform fast track jump without being affected by the eccentric quantity of the disk, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to speeding up track jumps of a tracking servo in an optical disc drive device.

[Prior Art] Tracking servo in an optical disc drive device is a servo in the radial direction of the disc for irradiating laser light along the grooves of the optical disc. Disturbances caused by misalignment or roundness of the central axis of the disk, or axial runout of the motor affect the tracking servo as eccentricity. Therefore, it is necessary to apply tracking servo to follow the amount of eccentricity. In addition, the slide system on which the optical head is mounted also uses a tracking actuator (a movable part with an objective lens) to remove low frequency components of eccentricity.
The movement of this actuator directs the laser beam onto the grooves of the optical disk) and the cooperative servo system (multiple movable systems move simultaneously to apply servo). Hereinafter, tracking servo refers to cooperative servo.

On the other hand, track jump refers to moving from the current groove position where the tracking servo is applied to a groove in the inner or outer diameter direction.The moving operation in this case is as follows. While keeping the focus servo (focus control) on, first turn off the tracking servo, move the radial movable part by the amount of the movement target, and then turn on the tracking servo again.

[Problems to be Solved by the Invention] However, in track jumping, it is very difficult to jump a large number of tracks at a time due to the poor positional accuracy of the center component and slide.

Therefore, the track jump is usually performed one time at a time, and this is repeated a set number of times to jump to the target position.

However, with this method, the response of the slide system was poor, so in order to stabilize the servo system, track jump intervals had to be set at 4 msec, resulting in the problem that it took a long time to jump several hundred tracks. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tracking servo device that increases the speed of track jumps in an optical disk drive.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a high-speed processor and a signal for converting the output from this processor into an analog signal to drive a tracking actuator and a slide motor. an analog-to-digital converter for converting the tracking error signal and the drive current of the tracking actuator into digital signals for monitoring by the processor; and a zero-crossing point of the tracking error signal. a slide encoder that outputs pulses proportional to the rotation speed of the slide motor; a spindle encoder that outputs pulses that are biased to the rotation speed of the spindle motor; and a tracking error detected by the output of the comparator. a counter circuit that counts the number of zero crossings of the signal and also counts the number of revolutions of the slide motor and the number of revolutions of the spindle motor; a switch that is controlled on and off by the processor and turns on or off the tracking servo; The present invention is characterized in that it includes an adder that adds the output of this switch to the drive signal of the tracking actuator.

[Operation] In the present invention, n-track jump is performed by the following procedure.

(1) The tracking error signal is monitored to detect a tracking pull-in point, and the number m of zero-crossings of the tracking error signal occurring between the two tracking pull-in points is determined by a counter circuit.

(2) Turn on the tracking servo at the pull-in point and monitor the actuator coil current via an analog-to-digital converter.

(3) Next, keep the focus servo on and turn off the tracking servo at the pull-in point.

(4) Drive the actuator with the coil current obtained in (2) above, hold the position, and turn off the tracking servo.

(5) Drive the slide motor while counting the comparison signal based on the pull-in point to track pitch x n (
n is the number of track jumps). The number of output pulses P of the comparison signal counted during movement and the number of pulses from the spindle encoder are counted to determine the counted number Q of two-phase pulses.

(6) Turn on the tracking servo at the pull-in point and keep the camera still on that track.

(7) In the processor, find the remaining number of jumps Y based on the following equation.

Y=n-[P-mXQ] (8) For the remaining number of jumps, repeat one track jump at a time.

[Example code] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of an embodiment of a tracking servo device according to the present invention. In FIG. Digital converter
An analog converter (hereinafter referred to as a DA converter) 3 is an adder that adds the output of the DA converter and a tracking error signal. Note that the tracking error signal is generated from the optical system when there is an abnormality in tracking.

4 is a current output type power amplifier for driving a tracking actuator, 5 is a tracking actuator for moving the optical head in the radial direction of the disk, 6 is a sense resistor for converting the tracking actuator current into voltage and detecting it, and 7 is a power amplifier for driving a tracking actuator. An analog-to-digital converter (hereinafter referred to as an AD converter) controlled by a processor, 8 a power amplifier for driving the slide motor, and 9 a slide motor that slides (moves) the disk in the radial direction. It is a drive motor for.

An encoder 10 is connected to the rotating shaft of the slide motor and detects the position based on the number of rotations of the slide motor, and outputs a pulse corresponding to the slide position.

11 is a comparator that detects zero crossing of the tracking error signal.

13 is a spindle motor for rotating the optical disk, and 14 is a spindle encoder connected to the rotating shaft of the spindle motor and outputting pulses corresponding to the number of rotations thereof.

12 is a counter circuit that counts the number of pulses output from the comparator 11, that is, the number of zero crosses, counts the number of pulses output from the slide encoder 10, and counts the number of pulses output from the spindle encoder 1.
The number of output pulses of 4 is counted respectively.

15 is a switch for turning on and off the tracking servo, and this switch is controlled by the CPUI.

The operation in such a configuration will be explained next.

The tracking servo system is controlled by the CPUI. Data from the CPU provided via the DA converter 2 drives the slide motor 9 via the power amplifier 8 . The position of the slide motor is detected by counting pulses from the slide encoder 10 with a counter circuit 12, and the tracking actuator 5 is driven to move the head onto the disk.

To operate the tracking servo, do the following. The tracking error signal is monitored by the AD converter 7, and when the error signal crosses zero, the switch 15 is turned on to operate the tracking servo. At this time,
The tracking error is monitored by the AD converter 7, and only the low frequency component of the error signal is detected by the CPUI.
The correction is made by driving the slide motor 9 through the DA converter 2.

FIG. 2 is a diagram showing a tracking error signal when only focus servo (focus control) is applied. When the disk rotates, if there is eccentricity, it crosses the surface of the disk, so the error signal waves as shown in figure (a).The place where the error signal crosses zero at a wide interval is the maximum of the eccentricity component. When the groove is on the inner or outermost track, the speed of crossing the groove is the slowest. It can be seen that the wavy error curve is a repetitive signal for one rotation of the disk. The position where the tracking servo is turned on is the pull-in point PL, P2 (the position with a wide zero cross interval,
This is done at the zero crossing point when going from positive to negative or from negative to positive. This is because the tracking servo stably operates on the groove.

The signal shown in FIG. 4B is a signal (referred to as a two-phase pulse) from the encoder of the spindle motor, and one pulse is generated for one rotation of the motor.

The signal shown in FIG. 3(c) is an output signal obtained by comparing the tracking error signal with the zero level by the comparator 11.

Next, high-speed track jump (one track jump)
The sequence will be explained.

(1) The tracking error signal shown in Fig. 2(a) is
It is monitored by the D converter 7 and the tracking pull-in points Pi and P2 at the widest zero-cross interval are found. This point P1 corresponds to the two-phase pulse shown in the same figure (c) for the two-phase pulse shown in the same figure (b).
The position of the pull-in point is known by detecting the number of currants in the comparison signal shown in . This pull-in point is the innermost or outermost circumference of the eccentric component. The position of this point is almost constant regardless of the diameter of the disk.

The counter 12 shown in FIG. 1 determines how many pulses of the comparison signal shown in FIG. 2(C) arrive between the pull-in points P1 and 22 in FIG. 2(a). Let this be m. This number of pulses corresponds to the amount of latent core in one rotation of the disk, and usually the number of pulses per one rotation is almost constant regardless of the diameter of the disk (with an error of ±1 count).

(2) Turn on the tracking servo at the pull-in point and keep the still at the pull-in point.The groove on the disc is spiral-shaped! (Spiral type), so when the disk is rotating, it performs a track jump once per rotation in the inner direction of the radius and returns to the original track. This is called a still.

During cooperative servo, the slide system follows the eccentricity of the disk, but the slide system does not move sufficiently at the pull-in point with the largest displacement. At the outermost periphery), the tracking actuator is at the very end of its movable range.

The coil current of the tracking actuator (detected as a voltage by the sense resistor 6) at this pull-in point is monitored via the AD converter 7 and measured in advance.

(3) To perform a track jump, leave the focus servo on and turn off the tracking servo at the pull-in point.

(4) Immediately thereafter, the actuator coil current obtained in the above (2) is outputted via the DA converter 2 to hold the actuator position.

The slide system is likely to move even after the servo is turned off due to its large inertia, but the point at which tracking is turned off is the innermost or outermost circumference, which is the point where the slide system is restrained, so there is no such movement.

If tracking is turned off in this manner, the track at the pull-in point will be the same as the track with tracking turned on. Therefore, the same track can always be found even in the servo-off state regardless of eccentricity.

(5) Move the slide by the track pitch (1.6 μm) x n while counting the comparison signal based on the pull-in point. At this time, the moving distance of the slide is determined by counting the encoder pulses from the slide encoder 10 with the counter circuit 12. CPU 1 performs position control.

The number of comparison signals P that is not counted during the movement, and the number of pulses from the spindle encoder that indicate how many rotations have been made during this period are counted to determine the Z-phase count number Q.

In addition, the accuracy of slide position control is poor, ±20 μm (±
13 tracks).

(6) Turn on the tracking servo at the pull-in point and perform still on that track.

(7) The processor calculates the remaining number of jumps Y using the following equation.

Y = n - (P - m The maximum number of jumps is 13. If there are a maximum of 13 track jumps, 1
Since there is no problem in terms of time even if the jump for one track is repeated 13 times, the jump is repeated.

This completes the high-speed track jump of n tracks.

This high-speed track jump is effective for track jumps of 20 tracks or more, and within that range, it is better to perform the conventional one-track-at-a-time track jump sequence.

[Effects of the Invention] As explained in detail above, according to the present invention, the system is not affected by the eccentricity of the disk or the position control accuracy of the slide system.
Enables high-speed track jumps. This has the effect of speeding up various measurements that previously took time. Furthermore, in the past, once the tracking servo was turned off, it was very difficult to perform tracking on the same track, but the present invention has the effect that this is easy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a tracking servo device according to the present invention, and FIG. 2 is a diagram showing waveforms of various parts when only focus servo (focus control) is applied. 1... High-speed processor, Tsusa, 2... DA converter, 3...
... Adder, 4... Power amplifier for driving tracking actuator, 5... Tracking actuator, 6... Sense resistor, 7... AD converter, 8...
Power amplifier for driving slide motor, 9... Drive motor, 10... Niji 1 coder, 11... Comparator, 13
... Spindle motor, 14... Spindle encoder, 12... Counter circuit, 15... Switch. Figure 1. Endle encoder 7+ Figure

Claims (1)

[Claims] A tracking servo device that performs track jumps in an optical disk drive device, which includes a high-speed processor, converts the output from the processor into an analog signal, and outputs a signal for driving a tracking actuator and a slide motor. a digital-to-analog converter for converting the tracking error signal and the drive current of the tracking actuator into digital signals for monitoring by the processor; and an analog-to-digital converter for detecting the zero-crossing point of the tracking error signal. a slide encoder that outputs pulses proportional to the rotation speed of the slide motor; a spindle encoder that outputs pulses proportional to the rotation speed of the spindle motor; and a zero cross of the tracking error signal by the output of the comparator. a counter circuit that counts the number of rotations of the slide motor and the rotation number of the spindle motor; a switch that is controlled on and off by the processor to turn the tracking servo on or off; A tracking servo device comprising an adder for adding an output to a drive signal of the tracking actuator, and performing an n-track jump according to the following procedure. (1) The tracking error signal is monitored to detect a tracking pull-in point, and the number m of zero-crossings of the tracking error signal occurring between the two tracking pull-in points is determined by a counter circuit. (2) Turn on the tracking servo at the pull-in point and monitor the actuator coil current via an analog-to-digital converter. (3) Next, keep the focus servo on and turn off the tracking servo at the pull-in point. (4) Drive the actuator with the coil current obtained in (2) above, hold the position, and turn off the tracking servo. (5) Drive the slide motor while counting the comparison signal based on the pull-in point to track pitch × n (n
is the number of track jumps), and the count number Q of Z-phase pulses is determined by counting the output pulse number P of the comparison signal counted during the movement and the number of pulses from the spindle encoder. (6) Turn on the tracking servo at the pull-in point and keep it still on that track. (7) In the processor, find the remaining number of jumps Y based on the following equation. Y=n-[P-m×Q] (8) For the remaining number of jumps, repeat one track jump at a time.