JPH05128552A - Tracking servo circuit of optical disk player - Google Patents

Abstract

PURPOSE:To provide a tracking servo circuit which is capable of reducing a circuit scale and maintaining a high speed sampling rate by saving DSP steps. CONSTITUTION:An address to which a factor RAM 32 makes an access in response to the presence of a brake ON command is changed. A further attempt is made to change the setting of a factor value of a digital filter 31, responding to factor data housed in that address. This construction makes it possible to install both HPTZC PF and anti-shock BFP functions to a single digital filter 31 and form both filters on the same DSP steps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo circuit for an optical disk player, and more particularly to a tracking servo circuit for an optical disk player having an anti shock function as a vibration countermeasure.

[0002]

2. Description of the Related Art As a tracking servo circuit in an optical disc player, for example, a CD player, a conventional servo circuit shown in FIG.
The configuration shown in is known. In the figure, the recorded information on the disk 1 is read by an optical pickup 2, and the read RF signal is supplied to a demodulation system via an RF amplifier 3 and digitized by an A / D converter 4 to detect a track crossing detection circuit. 5 is supplied.

A tracking error (TE) signal generation circuit 6 generates a tracking error signal having a so-called S-shaped curve characteristic based on the output of the pickup 2 by a known generation method such as the three-beam method. This tracking error signal passes through the A / D converter 4 and then the servo filter 7, anti-shock BPF (band pass filter).
8 and HPTZC HPF (high-pass filter) 9. The tracking error signal passed through the servo filter 7 is supplied to the PWM generator 10.

As shown in FIG. 5, the PWM generator 10 outputs the tracking error value passed through the servo register 21 in the servo ON state and the jump value from the jump value register 22 in response to the track jump command during the track jump operation. The PWM pulse generation circuit 2 is selected by the selection switch 23, and is selected via the AND gate 24.
In the servo-on state, the tracking error signal is pulsed according to the signal level and then supplied as a drive signal to the tracking actuator in the pickup 2 via the actuator driver 11. As a result, the position control of the information reading light spot with respect to the track (pit row) of the disc 1 in the disc radial direction is performed.

On the other hand, μCPU (microcomputer)
When a track jump command is issued from 12, P
The WM generator 10 generates a jump pulse having a pulse width corresponding to the number of tracks to be skipped by the information reading light spot based on the jump value output from the jump value register 22 and applies it to the tracking actuator via the actuator driver 11. To do. During this jump operation, the servo is turned off.

In the antishock BPF 8, only the frequency component of the specific band of the tracking error signal is extracted, and the extracted frequency component of the specific band is supplied to the comparator 13 and compared with a predetermined reference level. This comparison output is supplied to the servo filter 7 as a gain switching signal. As a result, it is determined that vibration occurs when an amplitude equal to or higher than the reference level exists in a specific frequency band of the tracking error signal, and control is performed to increase the gain of the servo filter 7.

That is, particularly in a portable type CD player, when the vibration is generated, the vibration is detected and the gain of the servo filter 7 is increased to make it difficult for the servo to come off. This is the so-called antishock function. Whether or not to activate the anti-shock function is selected depending on whether or not an anti-shock ON signal for activating the anti-shock BPF 8 is output from the μCPU 12.

The tracking error signal is HPTZ.
The phase advances when passing through the HPF 9 for C, and is sliced by the slicing circuit 14 whose slice level is zero level, so that HP (High-pass) TZC (Tracking Zero Cro).
ss) signal. This HPTZC signal is supplied to the edge detection circuit 15 and its edge is detected. This HPT
The ZC edge signal is sampled by the sampling circuit 17 at a high level mirror signal generated by the mirror signal generation circuit 16 on the mirror surface between the tracks of the disk 1. This sampling signal is the PWM generator 1
0 is supplied as a tracking cancel signal.

Referring again to FIG. 5, an inverted signal of the track jump command signal inverted by the inverter 26, μCPU
The brake ON signal issued from 12 and the track cancel signal output from the sampling circuit 17 are AN
It has three inputs to the D gate 27, and the output of the AND gate 27 is supplied to the AND gate 24 as a gate control signal as a mask signal. That is, in the period in which the track jump command is not issued, the brake ON command is issued, so that the tracking cancel signal becomes valid and acts as a mask signal.

As a result, as shown in FIG. 6, the tracking cancel signal becomes valid immediately after the track jump, and only the tracking drive signal waveform having the polarity corresponding to the track jump direction is masked by the mask signal accompanying this. To do. As a result, immediately after the jump,
A force in the direction opposite to the track jump direction, that is, a braking force acts on the tracking actuator.

During the track jump operation, the track crossing detection circuit 5 detects that the information reading light spot has crossed the track on the basis of the RF signal and the tracking error signal, and the countout signal Cout is issued at the time of detection. Be done. The μCPU 12 detects the jump destination track by counting the count-out signal Cout.

[0012]

By the way, in the above-mentioned digital tracking servo circuit, the anti-shock BPF 8 is independently provided with a unique DSP (Digital Signa).
l Processor) step, the DSP at the current sampling rate (for example, 88.2 kHz)
Since there are not enough steps, the sampling rate is reduced to earn DSP steps. However, the reduction of the sampling rate causes the circuit configuration to become complicated,
In addition, when integrated into an IC, the performance of the entire IC tends to decrease.

Therefore, it is an object of the present invention to provide a tracking servo circuit for an optical disk player, which enables the circuit size to be reduced by saving the DSP steps and at which the sampling rate can be maintained at a high speed.

[0014]

A tracking servo circuit according to the present invention includes a digital filter for selectively deriving a frequency component of a specific band of a tracking error signal and its high frequency component according to a coefficient value to be set, Gain control means for controlling to increase the servo gain when the signal level of the frequency component of the specific band is equal to or higher than a predetermined reference level, and applying the braking force to the tracking actuator using the high frequency component when a brake ON command is issued. The actuator control means and the coefficient setting means for setting a predetermined coefficient value for the digital filter depending on whether or not the brake ON command is generated are provided.

[0015]

In the tracking servo circuit having the anti-shock function, the HPTF for HPTZC and the anti-shock are changed to a single digital filter by changing the setting of the coefficient value of the digital filter according to the presence or absence of the brake ON command. Both functions of the BPF for use are provided, and both filters are formed on the same DSP step. As a result, DSP steps can be saved, the circuit scale can be reduced, and the sampling rate can be maintained at a high speed.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, and shows only the configuration of the main part of a tracking servo circuit according to the present invention. In the figure, a single digital filter 31 that receives a tracking error signal is used as the anti-shock BPF 8 and HPTZC H in FIG.
It is provided corresponding to PF9. The digital filter 31 has a basic IIR type digital filter as a basic structure, and has a configuration in which the coefficient value of each multiplication coefficient can be arbitrarily set according to the coefficient data output from the coefficient RAM 32.

The coefficient RAM 32 reads the coefficient data stored at the address designated by the address signal issued from the address generator 33 and outputs it to the digital filter 31. The address generator 33 receives the anti-shock BPF and H according to the address switching signal.
The address signals of two systems corresponding to the HPF for PTZC are output to the coefficient RAM 32.

On the other hand, the μCPU 12 outputs 4 bits (D1 to D) for controlling the tracking servo.
The commands of 4) are supplied, and these commands are stored in the command register 34. Of the commands D1 to D4, D4 is an anti-shock function, D3 is a brake application, and D2 and D1 are tracking gain UP control commands.

That is, the commands (D4 to D1) are
Antishock ON when (10 **), (0 **)
*) Anti shock OFF, (* 1 **) brake ON, (* 0 **) brake OFF,
Tracking gain normal when (** 00), (*
When * 01), (** 10), and (** 11), the tracking gain UP is controlled.

Then, the D4 command signal and the inverter 3
AND with 2 input of D3 command signal after inversion at 5
The output of the gate 36 becomes an antishock ON signal and is supplied to the address generator 33 as an address switching signal. Further, the D3 command signal becomes the brake ON signal as it is, and the D2 and D1 command signals also become the tracking gain UP signal through the OR gate 37.

As a result, when an antishock ON command (10 **) is issued, at the same time as the antishock ON signal is output, the address generator 33 is output.
Generates an address signal corresponding to the anti-shock BPF, and coefficient RAM 32 outputs coefficient data designated by the address signal to the digital filter 31. As a result, the digital filter 31
As shown in FIG. 2, an anti-shock BPF including a combination of a front-stage HPF and a rear-stage LPF is configured to extract a frequency component in a specific band of the tracking signal.

On the other hand, brake ON command (* 1 **)
Is issued, the anti-shock ON signal disappears at the same time that the brake ON signal is output. Therefore, the address signal corresponding to the HPTF for HPTZC is generated from the address generator 33, and the address from the coefficient RAM 32 is generated. The coefficient data designated by the signal is output to the digital filter 31. As a result, as shown in FIG. 3, the digital filter 31 constitutes an HPTZC HPF that makes only the preceding HPF effective, and extracts the high-frequency component of the tracking signal.

That is, the digital filter 31 has both functions of the anti-shock BPF and the HPTZC HPF, and both filters are formed on the same DSP step. When the anti-shock is ON, the anti-shock BPF is provided. As the brake is ON, H
It acts as an HPF for PTZC. Note that FIG.
3 and FIG. 3, each multiplication coefficient K1 to K10 of the multiplier
Is a predetermined coefficient value set based on the coefficient data from the coefficient RAM 32.

By the way, the anti-shock function has a role of putting the servo filter 7 into a gain-up state,
This means that the anti-shock function is unnecessary when the gain is already increased.
Further, when the brake is turned on immediately after the track jump, the servo filter 7 must be in the gain UP state. Therefore, the tracking gain UP command is generally sent from the μCPU 12 at the same time as the brake ON command.

That is, since the servo filter 7 is originally in the gain UP state while the command is brake ON, the anti-shock BPF is unnecessary during this period. In other words, both the HPTZC HPF required when the brake is turned on and the antishock BPF required when the tracking gain is in the normal state do not act at the same time.

In the present invention, paying attention to this point, when the anti-shock is turned on, the digital filter 31 is made to function as the anti-shock BPF, but even if the anti-shock ON command (10 **) is activated, the brake is applied. If the ON command (* 1 **) becomes active, the digital filter 31 does not function as the anti-shock BPF, and the HPTZC HP
It functions as F.

As described above, even if the anti-shock ON command is active, the HPTZ for HPTZC and the BPF for anti-shock are issued by the command of brake ON.
It is possible to form both filters on the same DSP step by selectively using, which can save a large DSP step, and focus, sled, and other servo functions can be performed with only 64 DSP steps. Since 64 steps can be realized in total, the circuit scale can be reduced and the sampling rate can be maintained at a high speed (for example, 88.2 kHz).

In the above embodiment, the case where the present invention is applied to the CD player has been described, but the present invention is not limited to the application to the CD player, but can be applied to all players of optical discs such as video discs. Is.

[0029]

As described above, according to the present invention,
Since the setting of the coefficient value of the digital filter is changed depending on whether or not the brake ON command is generated, a single digital filter has both the HPTF for HPTZC and the BPF for antishock and the same DSP. Since both filters can be formed on the step, DS
The P steps can be saved, the circuit scale can be reduced, and the sampling rate can be maintained at a high speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, showing only a configuration of a main part of a tracking servo circuit according to the present invention.

FIG. 2 is a block diagram of a digital filter as an antishock BPF.

FIG. 3 is a configuration diagram of a digital filter as an HPTF for HPTZC.

FIG. 4 is a block diagram showing an example of a configuration of a conventional example of a tracking servo circuit.

FIG. 5 is a block diagram showing an example of a configuration of a PWM generator.

FIG. 6 is a waveform diagram showing a correspondence relationship between a tracking drive waveform and each command.

[Explanation of symbols]

 1 Disk 2 Optical Pickup 5 Track Crossing Detection Circuit 6 Tracking Error Signal Generation Circuit 7 Servo Filter 8 Anti-Shock BPF 9 HPTZC HPF 10 PWM Generator 12 Microcomputer (μCPU) 21 Servo Register 22 Jump Value Register 25 PWM Pulse Generation Circuit 31 Digital Filter 32 Coefficient RAM 33 Address Generator 34 Command Register

Claims (1)

[Claims] 1. A tracking servo circuit of an optical disc player, comprising a tracking actuator for displacing an information reading light spot in a disc radial direction with respect to a track of the optical disc, and drivingly controlling the tracking actuator according to a tracking error signal. A digital filter that selectively derives a frequency component of a specific band of the tracking error signal and its high frequency component according to a coefficient value that is set, and a signal level of the frequency component of the specific band is equal to or greater than a predetermined reference level. , A gain control means for controlling to increase the servo gain, an actuator control means for applying a braking force to the tracking actuator by using the high frequency component when a brake ON command is issued, and a generation of the brake ON command. Tracking servo circuit characterized by comprising a coefficient setting means for setting a predetermined coefficient value to the digital filter in accordance with the free.