JPH0215430A - Loop gain setting method for tracking servo loop - Google Patents

Abstract

PURPOSE:To excellently execute a tracking control by turning off a tracking servo loop near an intermediate periphery, suppressing the frequencies of a tracking error signal, detecting its amplitude, and setting the gain of the tracking servo loop. CONSTITUTION:When the information reading optical spot of a pickup 2 arrives at an intermediate peripheral track, it is controlled so that a relative speed may be zero, and after the gain of an error amplifier 16 is set based on a p-p value of the tracking error signal, the tracking servo loop is made into a closed condition. Thus, the value of the loop gain can be made optimum with respect to the mean value of a reflectivity, etc., on each point in the whole recording area of a disk 1. Consequently, the excellent tracking control can be executed on any position of the recording area of the disk 1.

Description

TECHNICAL FIELD The present invention relates to a loop gain setting method for a servo loop in a tracking servo device.

BACKGROUND TECHNOLOGY Playback of recorded information on video discs, digital audio discs, etc., or D RA W (DlrcctR
ead After Write) disc, E-DR
In a disk recording and/or reproducing device that records and reproduces information on an AW disk, etc., a tracking servo device is essential to make the information reading point of the pick-up disk accurately follow the recording track of the disk. . In this tracking servo device, fluctuations occur in the loop gain due to variations in the power of the light source such as a laser diode, the reflectance of the disk, and the shape of the pits, causing fluctuations in the band of the servo loop. This may cause a decrease in performance or oscillation.

Therefore, we used a variable gain amplifier as an error amplifier,
The pp value of the error signal obtained in the oven state of the servo loop is detected, a gain constant is set based on this detected pp value, and the gain of the variable gain amplifier is controlled according to this gain constant. A method for setting the loop gain of a servo loop in a tracking servo device has already been devised and disclosed in Japanese Patent Laid-Open No. 106003/1983.

However, in the loop gain setting method of the servo loop in this conventional tracking servo device,
Each time a search is performed, the p-p value of the error signal is detected, and the gain of the variable gain amplifier is controlled according to the set gain constant. However, the loop gain value may not always be the optimal value at positions far from the searched disk position, and the servo loop may become unstable. Something happened.

Summary of the Invention The present invention has been made in view of the above points, and includes:
It is an object of the present invention to provide a loop gain setting method for a tracking servo loop that can set the loop gain of a tracking servo loop so that good tracking control is possible at any position on a recording disk.

In order to achieve the above object, in the tracking servo loop loop gain setting method according to the present invention, the information reading point of the pickup is moved to the middle track located between the innermost track and the outermost track in response to a command. Then, near this middle track, the tracking servo loop is turned off, while the pickup feed mechanism is driven to suppress the frequency of the tracking error signal, the amplitude of the tracking error signal is detected, and the tracking servo loop is activated based on this amplitude. I am trying to set the gain.

Further, it is preferable that the above-mentioned command is issued immediately after the play command immediately after the disc is loaded.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, recorded information on a disc 1 is read by a pickup 2. As shown in FIG. The pickup 2 has various built-in actuators such as a laser diode, an objective lens, a photodetector, and a tracking actuator that deflects the information reading optical spot (information reading point) of the pickup 2 in a direction perpendicular to the recording track (disc radial direction). There is.

The output of the pickup 2 is amplified by a head amplifier 3 and then supplied to a tracking error signal generation circuit 4 and a demodulation processing circuit 5. The demodulation processing circuit 5 performs analog-to-digital conversion processing on the RF multiplied signal outputted from the pickup 2, for example, and then performs predetermined demodulation processing to obtain recording data and address data indicating the recording position of the obtained recording data. It is configured to obtain. Further, the tracking error signal generation circuit 4 is configured to generate a tracking error signal according to the relative position of the information reading optical spot of the pickup 2 with respect to the recording track, for example, by a so-called sampled servo method. Regarding the sampled servo system, please refer to the patent application filed in 1986.
3-93882.

The tracking error signal generated by the tracking error signal generation circuit 4 is supplied to the linear motor control circuit 7.

The linear motor control circuit 7 is supplied with the outputs of the speed detection circuit 8 and the speed detector 9 as well as the low frequency components of the tracking error signal. The speed detection circuit 8 is supplied with the output of a zero cross comparator 10 that compares the tracking error signal with the zero level and generates a pulse that forms a binary signal according to the comparison result.
is configured to output, for example, a signal having a level corresponding to the frequency of the output pulse of the zero-cross comparator 10 as the speed detection signal a. The speed detector 9 is composed of, for example, a plurality of magnetic poles formed on the movable element of the linear motor 11 and a speed detection coil provided on the stator so as to face the magnetic poles.
A speed detection signal having a level corresponding to the relative speed of the movable element is generated.

The linear motor control circuit 7 includes a microcomputer 15
The structure is such that the following control is performed in response to first and second speed control commands issued from the motor. That is, the first
When neither the second speed control command nor the second speed control command is issued, the near motor control circuit 7 drives the linear motor 11 according to, for example, the low frequency component of the tracking error signal. At this time, the pickup 2 is driven in the radial direction of the disk 1 by the linear motor 11, and the tracking actuator in the pickup 2 is controlled so as to be located at the midpoint of the movable range. Further, when the first speed control command is issued, the linear motor control circuit 7 detects and detects the relative speed of the information reading optical spot of the pickup 2 in the direction perpendicular to the track using the speed detection signal a obtained from the tracking error signal. The linear motor 11 is driven in the specified direction so that the relative speed obtained becomes the specified speed. Further, when the second speed control command is issued, the linear motor control circuit 7 detects the relative speed of the pickup 2 in the direction perpendicular to the track by a speed detection signal corresponding to the speed of the linear motor 11, and the detected relative speed is specified. The linear motor 11 is driven in the specified direction to achieve the specified speed.

Further, the tracking error signal is amplified by an error amplifier 16 whose gain is variable, and then the loop switch 1
7. The signal is supplied to a tracking actuator in the pickup 2 via one equalizer circuit and a drive amplifier 20, forming a tracking servo loop. The tracking actuator is driven by this tracking servo loop based on the level of the tracking error signal, so that the information reading light spot accurately follows the recording track. Furthermore, the equalizer circuit 22 converts the low frequency components of the tracking error signal into the linear motor control circuit 7.
is applied to drive the linear motor 11.

Further, the tracking error signal is supplied to the A/D converter 18, and data corresponding to the level of the tracking error signal is generated and supplied to the microcomputer 15 including a processor, ROM, RAM, etc. The microcomputer 15 further includes output pulses from the zero-cross comparator 10, output from a detector 21 for detecting that the pickup 2 has reached the innermost circumferential position of the disk 1, and commands corresponding to key operations on the operating section (not shown). etc. are supplied.

In the microcomputer 15, the processor is RO
The input signal is processed according to a program stored in advance in M, and various commands and data are sent to the loop switch 17, linear motor control circuit 7, error amplifier 16, etc.

In the above configuration, the operation of the processor in the microcomputer 15 will be explained with reference to the flowchart in FIG.

When a play command is issued during execution of a main routine, etc., the processor moves to step S1 and sends data indicating the inner circumferential direction and a predetermined speed to the linear motor control circuit 7 along with a second speed control command. Step S1
), it is determined whether the pickup 2 has reached the innermost circumference (step S2). If it is determined in step S2 that the innermost circumference has not been reached, the processor moves to step S1 again. When it is determined in step S2 that the innermost circumference has been reached, the processor selects a circuit (
A supply start command is sent to the loop switch (not shown) to turn on the laser diode (step S3), and an on command is sent to the loop switch of the focus servo loop (not shown) to turn on the focus servo (step S4). . Next, data indicating the outer circumferential direction and data indicating a predetermined speed are sent to the processor linear motor control circuit 7 together with the second speed control command (step S5), and it is determined whether predetermined address data has been read (step S6). ).

If it is determined in step S6 that the predetermined address data has not been read, the processor moves to step S5 again. When it is determined in step S6 that the predetermined address data has been read, the processor nearer motor control circuit 7 is provided with a first speed control command, data indicating the outer circumferential direction, and the outermost track and innermost track of the disk 1. While calculating the distance to the address on the middle circumferential track in the middle of , data indicating the speed corresponding to the calculated distance is sent out (step S7).

Next, data indicating zero speed is sent to the processor linear motor control circuit 7 along with the first speed control command (step S8), and positive and negative peak values of the tracking error signal are collected by the output of the A/D converter 18, The difference (p-p value) between the collected positive and negative peak values is calculated (step S9).

Next, the processor generates a gain constant having a relationship as shown in FIG. 3 for the calculated p-p value using a ROM table or the like, and supplies data corresponding to the obtained gain constant to the error amplifier 16 (step 510). Next, the processor starts supplying an on command signal to the loop switch 17 (step 511) and closes the tracking servo loop.

Through the above operations, the relative speed of the information reading optical spot of the pickup 2 in the direction perpendicular to the track becomes as shown in FIG. By steps S1 and S2, the pickup 2 moves at a constant speed in the inner circumferential direction to the innermost circumferential position. When the pickup 2 reaches the innermost circumference position (time tI), the pickup 2 moves at a constant speed toward the outer circumference in steps S5 and S6 to a position where predetermined address data can be obtained. When pickup 2 reaches a position where predetermined address data can be obtained (time t2)
, the information reading optical spot of the pickup 2 is at step S.
7, the disk 1 is moved to a track halfway between the outermost track and the innermost track, but after the start of movement, the relative speed is accelerated until it matches the target speed, and then decelerated.

When the information reading optical spot of the pickup 2 reaches the middle track (time t3), the relative speed is controlled to be zero in step S8, and the frequency of the tracking error signal, that is, the relative speed is suppressed. works. At this time, the gain of the error amplifier 16 is set based on the pp value of the tracking error signal in step S9 and SIO. After the gain of the error amplifier 16 is set, the tracking servo loop is closed in step S11 (time t4).
.

As described above, in steps S9 and S10, the tracking error signal p-plii! The gain of the error amplifier is controlled based on the step S9 and the step S7 before the SIO, so that the position of the information reading optical spot of the pickup 2 is located between the outermost track and the innermost track. Since the movement is on the middle track, the gain of the error amplifier is set based on the p-p value obtained near the middle track, and the average reflectance etc. at each position in the entire recording area of the disc 1 is set. The loop gain value can be optimized for the value of
Good tracking control can be performed at any position in the entire recording area of the disc 1.

Further, in step S9, the relative speed of the information reading optical spot of the pickup 2 in the direction orthogonal to the track is controlled to be zero in the vicinity of the middle track, so the cross-track speed of the information reading optical spot of the pickup 2 is low. This allows the use of a low-speed A/D converter 18, eliminates the need for a peak hold circuit, and allows the peak value to be obtained with a simple configuration.

In the above embodiment, the relative speed of the information reading optical spot of the pickup 2 in step S7 is controlled using the speed detection signal a obtained from the tracking error signal.
However, the relative speed is controlled by a 16-track count pulse generated in the sampled servo system, that is, a pulse that is inverted every time the information reading light spot moves 16 tracks in the direction perpendicular to the track. You can.

Furthermore, in the above embodiment, each step after step S1 is executed every time a play command is issued, and the loop gain is set. Each step may be executed to set the loop gain, thereby eliminating redundant operations.

Effects of the Invention As detailed above, in the loop gain setting method of the tracking servo loop according to the present invention, the information reading point of the pickup is set on the middle track located between the innermost track and the outermost track in response to a command. The tracking servo loop is turned off near this middle track, while the pickup feed mechanism is driven to suppress the frequency of the tracking error signal, and the amplitude of the tracking error signal is detected, and tracking is performed based on this amplitude. Since the gain of the servo loop is set, it is possible to optimize the loop gain value for the average value of reflectance, etc. at each position in the entire recording area of the recording disk. Good tracking control can be performed at any position in the entire area. Furthermore, since the frequency of the tracking error signal is kept low, low-speed A/D
Even when a converter is used, the peak value of the tracking error signal can be captured without a peak hold circuit, and the circuit configuration can be simplified.

Further, it is preferable that the above-mentioned command is issued immediately after the play command immediately after the disc is loaded, since redundant operations are not performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the processor in the device shown in FIG. 1, and FIG. 3 is the relationship between the detected p-p value and the gain constant. FIG. 4 is a diagram showing how the relative speed of the information reading optical spot of the pickup 2 changes. Explanation of symbols of main parts 2...Pickup 4...Tracking error signal generation circuit 7...
...Linear motor control circuit 15...Microcomputer 16...
・Error amplifier

Claims (2)

[Claims] (1) A loop gain setting method for a tracking servo loop in an optical disc player, in which the information reading point of the pickup is moved to a middle track located between the innermost and outermost peripheries of the optical disc according to a command, and tracking While turning off the servo loop, detecting the amplitude of the tracking error signal while driving the pickup feed mechanism so as to suppress the frequency of the tracking error signal near the middle track, and adjusting the gain of the tracking servo loop based on the amplitude. A method for setting a loop gain of a tracking servo loop. (2) The loop gain setting method for a tracking servo loop according to claim 1, wherein the command is issued immediately after a play command immediately after a disk is loaded.