JPS63179476A - Tracking servo device - Google Patents

Abstract

PURPOSE:To reduce the track leading-in time at an information read point by applying speed servo in advance, reducing the relative speed in the disk radial direction of a light spot to reduce the frequency of a tracking error signal and then closing the loop of the tracking servo in closing the loop of the tracking servo. CONSTITUTION:In reaching the final search stage from a searching state while the tracking servo and speed servo are turned off, the speed servo is turned on for a prescribed time by a control means 42 at first or the speed servo is applied until the relative speed of the spot reaches a prescribed value or below. The frequency of a TE signal is lowered below the response frequency of the tracking servo system by the speed servo. Then the servo is switched into the tracking servo to lock in the tracking servo in a short time t2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking servo device for an information recording disk.

1. A light spot is irradiated onto an information recording disk (hereinafter referred to as a disk) on which information such as video and audio signals is recorded on concentric circles or spiral tracks, and the reflected or transmitted light is used to record information. There is an information reproducing device that reproduces information. In such an information reproducing apparatus, so-called tracking servo is performed based on a tracking error signal indicating the deviation between the track and the optical spot so that the optical spot accurately traces the optical spot.

Examples of such tracking servos are disclosed in Japanese Patent Application Laid-open No. 49-50951 using three beams, and Japanese Patent Application Laid-Open No. 49-60702 using one beam.

By the way, there is usually a shift, or eccentricity, between the center of disk rotation in the device and the center of the disk being played back, so if the tracking servo is not performed, the light spot will not cross the track. Become. As a result, the tracking error signal undergoes frequency modulation, and when the amount of eccentricity is large, the frequency modulation that the tracking error signal receives reaches from several KH2 to more than ten KH2. On the other hand, the response frequency of the tracking servo system is about 2KH2 to 3KH2, so if the tracking servo is operated in such a state, the tracking servo will be in a stable state (this is called a pull-in). The problem is that it takes a long time.

Accordingly, an object of the present invention is to provide a tracking servo device that can quickly draw a light spot onto a track.

In order to achieve the above object, the tracking servo device of the present invention is provided with speed servo means for controlling the relative speed of the optical spot on the disk in the radial direction in order to suppress the frequency increase of the tracking error signal, When the servo shifts from the OFF state to the ON state, first, velocity servo is performed for a predetermined time to lower the frequency of the tracking error signal, and then 1-racking servo is entered.

Support-5-1 Examples of the present invention will be described below. First, the overall configuration will be explained with reference to the block diagrams shown in FIGS. 1(A) and 1(B). The reflected light of two tracking light beams (not shown) is received and converted into two electrical signals, and a tracking error signal (hereinafter referred to as TE multiplied signal) obtained as a difference signal between these signals is generated at the zero crossing. The signal is supplied to the detection circuit 1 and the A/D converter 5. A
The output of the /D converter 5 is supplied to the signal processor 4 as a tracking servo signal. The TAB signal obtained as the sum signal of the above two signals is supplied to the light amount comparator 2. A zero-crossing detection circuit 1 generates a TZ-multiplied signal that inverts the output when the TE-multiplied signal level reaches the center level of the AC vibration, and a period detection counter 3 that measures the waveform width (between zero-crossing points) of this signal. and the direction detection circuit 6. The period detection counter 3 obtains a T signal indicating the TZ multiplied signal period by counting the clock signal of a constant period as the TZ multiplied signal timing control signal, and transmits this to the speed calculation means 4 of the signal processing processor 4.
Supply to 1. As shown in FIG. 1(B), the speed calculation means 41 includes a reciprocal calculation circuit 41a and a positive/negative sign imposition circuit 4.
1b and an equalizer calculation circuit 41C. The reciprocal calculation circuit 41a obtains the F signal representing the reciprocal of the period, that is, the frequency, by a predetermined calculation, and supplies this to the plus/minus sign addition circuit 41b. This F signal represents the absolute value of the speed error amount of the optical spot.

On the other hand, the TAB signal is waveform-shaped by a light amount comparator to become a signal, which is supplied to the direction detection circuit 6.

As mentioned above, the direction detection circuit 6 is separately supplied with the TE multiplied signal, and based on these signals, it determines in which direction the optical spot on the disk is moving in its radial direction. The FWD/REV signal, which has a high level when the spot is moving from the center of the disk toward the outer circumference and a low level when the spot is moving from the outer circumference toward the center, is added to the plus/minus sign adding circuit 41b.
supply to. The positive/negative sign adding circuit 41b
Based on the REV signal, positive or negative information is added to the value of the F signal to obtain a v1 signal, and a trunking actuator 10, which will be described later, operates to reduce the relative speed of the light spot. This {circle around (1)} signal is supplied to the equalizer performance circuit 7. The equalizer calculation circuit 7 determines whether the value of ■1 signal is relative to the tracking actuator,
The value is corrected so that it falls within an appropriate value for control, and the corrected value is supplied as a 2 signal to one input terminal of a signal switching circuit (not shown) of the control means 42. The output of the A/D conversion Va5 mentioned above is supplied to the other input terminal of this signal switching circuit.

The signal switch is controlled by control means 42.

The control means 42 controls the D/A in response to a jump command signal supplied from a control circuit (not shown) during a search operation, for example.
The data output to the converter 8 is cut off and the servo operation is stopped. Then, the slider servo system 100 is operated for rough adjustment of the pickup position. The slider 103 as a pickup moving means moves and the light spot reaches the vicinity of the target position, and the tracking error signal is sent to the D/A converter 101 by speed information of the slider 103 obtained from the low frequency component. When the means 42 detects that the moving speed of the slider 103 becomes less than a predetermined value due to a change in the output level of After a certain period of time,
In order to control the signal switching circuit to perform speed servo, for example, the v2 signal is relayed to the D/A converter 8 for a predetermined period of time, and the output of the A/D converter 5 is relayed to the D/A converter 8 to perform dominant position servo, that is, tracking servo. The signal supplied to the D/A converter is converted into a voltage signal with a level corresponding to its value and supplied to the drive circuit 9, resulting in a TD multiplied signal. This TO
The pickup tracking actuator 10 is driven by the signal, the light beam is deflected in the disk radial direction, and the position of the light spot is controlled. In this way, a speed servo system and a tracking servo system are constructed. In addition,
Even if the signal switching circuit described above is used as an adding circuit, a certain effect can be obtained.

Next, specific circuit examples of the zero cross detection circuit 1, the light amount comparator 2, and the direction detection circuit 6 will be explained with reference to FIGS. 2(A), (B), and (C).

Three light beam spots 81-S illuminated on the track
The reflected light of No. 3 enters the light receiving elements P1 to P3. The optical signal incident on the light receiving element P2 is converted into an electrical signal and supplied to a video demodulation circuit (not shown). Light receiving elements P1 and P
The output of No. 3 is supplied to an adder circuit 11 and a subtracter circuit 12, respectively. The output of the adder circuit 11 is supplied as a TAB signal to the light quantity comparator 2, and the waveform is shaped and supplied to the D input of the D flip-flop 13. The output of the subtraction circuit 12 is multiplied by TE and supplied to the zero cross comparator 1.
A TZ multiplied signal whose output is inverted every half cycle of the TE multiplied signal is obtained. The clock of this TZ multiplied signal flip-flop 13 (
(hereinafter referred to as GK) is supplied to the input terminal. As a result of the flip-flop 13 taking in the level of the TL signal as the Q output in response to the rise of the signal supplied to the GK input terminal, the Q output of the flip-flop 13 is such that the light spot is FWD as shown in FIG. 2(B). When moving in the REV direction, the level is low, and when moving in the REV direction, the level is high. The Q output of the flip 70 knob 13 becomes the FWD/REV signal.

Here, the flip 70 knob 13 corresponds to the direction detection circuit 6.

FIGS. 3(A) and 3(B) show other configuration examples of the direction detection circuit 6. In this example, since the moving direction of the spot is detected at both the rise and fall of the TZ multiplied signal, there is an advantage that the accuracy is improved accordingly. That is, in the case of the direction detection circuit shown in FIG. 2 (A>), the moving direction of the spot is detected every cycle of the TE signal q, but in this example, it is detected every half cycle. As a result of being able to shorten the period for speed detection, the accuracy of speed servo is improved.

In the circuit shown in FIG. 3(A), a GK low signal supplied from a clock oscillator (not shown), e.g.
It is a kHz pulse, and the GK of the D flip-flop 61
It is supplied via the input terminal and the inverter 62 to each CK input terminal of the D flip 70 tube 63,64. It is supplied to the D input terminal of the TZ double signal flip-flop 61, and to one input terminal of the 01 signal flip-flop 63 of its Q output, the exclusive 0R 65, and the switching control input terminal of the selector 66. The Q output of flip-flop 63 is applied as the Q2 signal to the other input of exclusive 0R65. The output of this exclusive 0R65 is supplied to the GK input terminal of the D flip-flop 67 as an R signal. flip 70 tube 6
The TL multiplied signal is supplied to the D input terminal of 7, and the Q3 signal which is its Q output and the 03 signal which is its 0 output are supplied to the selector 6.
6 ICO and 1C1 input terminals, respectively. When the Q1 signal is at a high level, the selector 66 selects the 03 signal and supplies it to the D input terminal of the 7-rip 70 tube 64.
When the signal is low, the Q3 signal is selected and applied to the D input of flip-flop 64. The FWD/REV signal is obtained at the 0 output of the flip 70 knob 64. FIG. 3(B) shows an example of the waveform of each signal when the light spot moves in the FWD direction. Movement in the REV direction is also detected in the same way.

A specific circuit example of the period detection counter 3 is shown in FIG. 4(A) and (
This will be explained with reference to B). The TZ multiplied signal from the zero cross detection circuit 1 and an oscillator (not shown) (for example, 220kHz)
The CK signal from the D flip-flop 31 is supplied to the D input terminal and the CK input terminal of the D flip-flop 31, respectively. The Q output of the flip 70 tube 31 is supplied as a TZDP signal to the D input terminal of the D flip 70 tube 32 and one input terminal of the exclusive 0R 33. An inverted GK multiplied signal whose output is inverted by an inverter 34 is supplied to the GK input terminal of the flip 70 tube 32, and its Q output is exclusively 0R3 as a TZDN signal.
3, one input of exclusive 0R35, and the D input of D flip-flop 36. A GK multiplied signal is supplied to the CK input terminal of the flip-flop 36, and its Q output is supplied as a TZDPI signal to the other input terminal of the exclusive 0R 35. The output of this exclusive 0R 35 is inverted by an inverter 37 to become a CLR signal, which is supplied to the clear input of a counter 38. The counter 38 counts the inverted GK multiplied signal pulses and supplies the counted value to the latch circuit 39, while resetting the counted value in response to the CLR signal. Since the CLR signal is generated approximately every half period of the TZ multiplied signal, the counter 38 updates the count value every zero-cross section of the TE signal. The latch circuit is formed by lucky D flip-flops, and their GK
The count value supplied to the D input is taken in in response to the ZE low signal supplied to the input terminal, and is supplied to the aforementioned speed reproduction circuit 41 as a T signal.

This is the output of the ZE low signal exclusive 0R33, which is generated immediately before the CLR signal and holds the above count value for approximately half a period of the TZ multiplied signal. The waveform of each signal is as shown in FIG. 4(B).

In this way, the cycle detection counter 3 detects the value of a half cycle of the tracking error signal.

A specific circuit of the reciprocal calculation circuit 41a will be explained with reference to FIG. The reciprocal calculation circuit 41a is constituted by a numerical calculation processor (not shown), and an arithmetic expression is selected according to the value of the input X, and the value of the reciprocal y is obtained by approximate value calculation.

In the example shown in FIG. 5, the reciprocal is obtained using five linear approximations, but the calculation characteristics of these can be appropriately set as necessary.

An example of the configuration of the equalizer calculation circuit 41C will be explained with reference to FIG. The v1 signal from the plus/minus sign adding circuit 41b is supplied to the coefficient circuit 411.

In the coefficient circuit 411, the coefficient is set to 0.0625, for example, and -Vl (n) is added to the value obtained by multiplying the current value Vl (n) of the 1 signal by the coefficient K in L, and the addition circuit 412
is supplied to one input end of the . The other input terminal of the adder circuit 412 is supplied with the output of a previous value calculation circuit consisting of a delay circuit 413 and a coefficient circuit 414. This addition circuit 4
The output v2(n) of 12 is supplied to a coefficient circuit 414.

The coefficient Ko of the coefficient circuit 414 is set to, for example, 0.935, and the value KO-v2(n) is set to the delay circuit 413.
supply to. The delay circuit 413 delays this value by a predetermined time to obtain the previous value Ko-v2(n-1), and its delay time characteristic Z is expressed as exp(s·T).

Here, ■ is the sampling period, for example, 31.778 μsec, which is a half period of the horizontal synchronization period of 63.5 μsec.
is set to Therefore, the ■1 signal supplied to this equalizer pancreatic circuit is v2 (n)= -vl (n)+
The arithmetic processing Ko-v2(n-1) is performed to produce a 2 signal, which is supplied to the D/A converter 8.

Regarding the difference between the operation of the tracking servo device of the present invention and the operation of the conventional tracking servo device, Fig. 7 (A)
This will be explained with reference to and (B).

First, Fig. 7 (A) is an example of a conventional device.If a search is performed with the tracking servo turned off, and then the tracking 1 novo is turned on at the final stage of the search, the TE low signal high frequency As a result, the convergence of the TD multiplied signal that drives the tracking actuator is slow, and it takes time (tl) to pull in the track.

FIG. 7(B) shows an example of the apparatus of the present invention. When the search is performed with the tracking servo and speed servo turned off, and the final stage of the search is reached, the control means 42 first controls the speed. The servo is kept on for a predetermined time or the velocity servo is performed until the relative velocity of the spot becomes less than a predetermined value. This speed servo causes the TE low signal frequency to drop below the response frequency of the tracking servo system. Thereafter, the tracking servo is switched to the tracking servo, and the tracking servo becomes in a leaky state in a short time (t2).

In this way, even if the tracking error signal has a high frequency due to eccentricity or vibration of the disk, the speed can be accurately detected every half period of the tracking error signal and based on this half period, and the tracking actuator can be adjusted based on this speed. Appropriate speed servo is applied to.

When detecting speed, the differential signal of the tracking error signal can be used as speed information, but such a method has the problem that the level of speed information changes due to changes in reflectance or scratches on the disk surface. On the other hand, according to the present invention, since the speed is detected based on the period of the tracking error signal, this problem is alleviated.

Note that it is possible to improve the position control accuracy of the pickup by using the detected speed servo signal as a control signal for the gear ridge servo in the seek operation.

In the embodiment, a tracking error signal is obtained using three beams, but a similar tracking error signal can also be obtained using one beam.

It is clear that the present invention can also be implemented in the so-called VHD system.

As explained above, in the tracking servo device of the present invention, when closing the tracking servo loop, speed servo is performed in advance to reduce the relative velocity of the optical spot in the disk radial direction. Since the frequency of the tracking error signal is lowered and the tracking servo loop is then closed, it is possible to shorten the track pull-in time at the information reading point.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1(A) and (B) are block circuit diagrams showing an embodiment of the present invention, and FIGS. 2(A), (B), and (C) are zero-cross detection circuit 1. FIG. 3 (A> and (B)) shows another example of the configuration of the direction detection circuit 6 and signal waveforms of each part thereof. 4(A) and 4(B) are diagrams showing a configuration example of the period detection counter 3 and the signal waveforms of each part thereof, FIG. 5 is a diagram showing the output characteristics of the reciprocal calculation circuit 41a, and FIG. , a block circuit diagram showing a configuration example of an equalizer calculation circuit, and FIGS. 7(A) and 7(B) are waveform diagrams for explaining the difference in operation between the conventional device and the device of the present invention. Explanation of symbols 1...Zero cross detection circuit 3...Period detection counter 6...Direction detection circuit 41...Speed calculation means Applicant Pioneer Corporation Agent Patent Attorney Motohiko Fujimura Akane? (21 (B) Book 5 concave, 75 concave, 4 concave)

Claims (3)

[Claims] (1) A pickup moving means for moving the information reading point of the pickup to the vicinity of the target recording track of the information recording disk, and tracking for obtaining a tracking error signal according to the amount of deviation in the disk radial direction of the information reading point of the pickup with respect to the recording track. error detection means; speed detection means for obtaining a speed signal proportional to the relative speed of the information reading point with respect to the recording track from the tracking error signal; A tracking servo device comprising: control means for controlling the moving speed of the information reading point in response to the above, and then controlling the position of the information reading point so as to reduce the amount of deviation. (2) The tracking servo device according to claim 1, wherein the speed detection means detects the relative speed based on a half cycle of change in the tracking error signal. (3) The tracking servo device according to claim 1, wherein the speed detection means detects the relative speed between each zero-crossing point of the tracking error signal.