JPH02168432A - Servo circuit for optical disk player - Google Patents

Abstract

PURPOSE:To prevent an abnormal motion of a feed motor, and to prevent runaway of a pickup by stopping the supply of an output signal from a phase compensation circuit to a servo circuit when focus servo is unlocked and a read signal reaches a prescribed voltage or below. CONSTITUTION:When focus servo is unlocked due to external disturbance such as vibration while a CD player reproduces a CD, the luminous quantity of a laser beam for reading a data made incident in photosensors 23, 24 is decreased, an output voltage of current/voltage conversion circuits 25, 26 is lowered and an RF signal is lowered than a prescribed level, then the signal of an H level is outputted from a comparator 28. Then a switch 30 is turned on by an output signal of the comparator 28. Thus, no tracking servo control signal is supplied to an LPF 21 and a feed motor 4 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a servo circuit for an optical disc player used for music reproduction or the like.

“Prior art” Figure 5 shows a conventional compact disc player (hereinafter referred to as C
FIG. 2 is a block diagram showing an example of the configuration of a D player.

In this figure, l is a compact disc (CD), 2
3 is the spindle and motor that rotationally drives the CDI, and 3 is the CD
An optical pickup uses a laser beam to read digital information recorded by pits on the signal recording surface of I. 4 is a feed motor that moves this optical pickup 3.

Further, 5 generates and outputs a focus error signal, a tracking error signal, and a frame synchronization signal from the read signal output from the optical pickup 3, and
This read signal is amplified and waveform-shaped to convert the digital data to EFM (Eight to Fourth).
R output as a Modulation) signal
The F amplifier 6 is a data processor that performs processing such as demodulating the EFM signal output from the RF amplifier 5, correcting and correcting code errors, and the digital signal output from the data processor 6 is processed by a DA converter (not shown) and It is output to an external speaker or the like as an analog audio signal via an audio circuit.

Furthermore, 7 is a system controller, which is composed of a CPU (central processing unit), a ROM in which programs used by the CPU are stored, a RAM for data storage, and 10 (input/output) board. 8 is a servo processor which, under the control of the system controller 7, uses focus error signals and tracking error signals output from the RF amplifier 5 to control focus adjustment (feed servo) of the optical pickup 3;
Tracking adjustment control (tracking servo) and feed R adjustment control (feed servo) of the feed motor 4;
The frame synchronization signal output from the RF amplifier 5 is used to output control signals for performing constant linear velocity control (spindle servo) of the spindle motor 2.

In addition, 9 uses a focus servo control signal output from the servo processor 8 to control the focus servo of the optical pickup 3 so that the focus of the objective lens of the optical pickup 3 always matches the signal recording surface of the CDI. A focus driver 10 drives an actuator for the optical pickup 3 using a tracking servo control signal output from the servo processor 8 so that the laser beam output from the optical pickup 3 always traces the signal track of the CDI. A tracking driver 11 drives an actuator for a tracking servo, using a feed servo control signal output from the servo processor 8, so that the laser beam output from the optical pickup 3 traces on a predetermined CDI signal track. A feed driver 12 drives the feed motor 4, and a spindle driver 12 uses a spindle servo control signal output from the servo processor 8 to drive the spindle motor 2 so that the rotation of the spindle motor 2 has a constant linear velocity. .

Next, of the four servos mentioned above, the tracking servo and the feed servo will be explained in detail.

FIG. 6 shows a specific example of a tracking servo and a feed servo. In this figure, parts corresponding to those in FIG. 5 are given the same reference numerals, and their explanations will be omitted. In this figure, 13 and ! 4 are each CDI
A foot sensor that converts the two tracking laser beams reflected by the ! into electrical signals. 5 is an actuator for tracking servo, 16 and 17 are photosensors 13 and !, respectively. 4 is a current/voltage conversion circuit that converts the output current into a voltage, and 18 is an error signal generation circuit that generates a tracking error signal from the output voltages of the current/voltage conversion circuits 16 and 17.

Further, 19 is a low-frequency boost circuit that increases the low-frequency gain of the frequency characteristic of the tracking error signal, and 20 is a phase compensation circuit that compensates the phase of the output signal of the low-frequency boost circuit 19 so that the tracking servo is stably applied. , 21 is a low-pass filter (LPF) that passes the output signal of the phase compensation circuit 20, that is, the low frequency component of the tracking servo control signal, and 22 is a low-pass filter (LPF) that compensates the phase of the output signal of the LPF 21 so that the feed servo is stably applied. This is a phase compensation circuit.

``Problems to be Solved by the Invention'' By the way, in the servo circuit of the conventional CD player described above, if a disturbance such as vibration is applied during CDI playback and the focus servo becomes disconnected or a track jump occurs, the tracking servo Disturbances occur in the low frequency components of the control signal.

The disturbance in the low frequency component of this tracking servo control signal passes through the LPF 21 and the phase compensation port 22 as it is, is output as a feed servo control signal, and is applied to the feed driver 11. This causes a problem in that the feed motor 4 moves abnormally in response to disturbances in the low frequency components of the tracking servo control signal.

Furthermore, due to abnormal movement of the feed motor 4, there is a problem in that the optical pickup 3 runs out of control toward the inner or outer circumference of the CDI and deviates from the data area of the CDI.

In addition, in models equipped with a return function that returns the playback position of the song to the position before the jump due to abnormal movement of the feed motor 4, there is a problem that the return time becomes longer.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a servo circuit for an optical disc player that can prevent abnormal movement of a feed motor when a disturbance occurs and can prevent runaway of an optical pickup. It is an object.

"Means for Solving the Problem" The first invention provides an optical pickup that reads data recorded on a disk, an amplifier that generates and outputs a tracking error signal from a read signal output from the optical pickup, and a tracking error signal. A low frequency boost circuit that increases the gain of the low frequency component of An optical disc player is equipped with a servo circuit that drives a feed motor using a comparator that outputs a signal when a read signal is less than a predetermined voltage, and one end of which is connected to the output terminal of a phase compensation circuit, and the other end of which is connected to a servo circuit that outputs a signal when the read signal is less than a predetermined voltage. It is characterized by comprising a resistor connected to the input terminal of the circuit, and a switch means having one end connected to the input terminal of the servo circuit, the other end being grounded, and turned on by the output signal of the comparator.

Further, a second invention is characterized in that in the first invention, the amount of increase in gain of the low-frequency boost circuit is limited by the output signal of the comparator.

Further, the third invention provides an optical pickup for reading data recorded on a disk, an amplifier for generating and outputting a tracking error signal from a read signal output from the optical pickup, and an amplifier for demodulating subcode data from the read signal. , a tstrA circuit that detects errors in subcode data and outputs an error detection signal, a low frequency boost circuit that increases the gain of the low frequency component of the tracking error signal, and a phase that compensates for the phase of the output signal of the low frequency boost circuit. In an optical disc player that includes a compensation circuit, a feed motor that moves an optical pickup, and a servo circuit that drives the feed motor using a low frequency component of an output signal of the phase compensation circuit, one end is connected to the output terminal of the phase compensation circuit. a resistor connected to the input terminal of the servo circuit, the other end of which is connected to the input terminal of the servo circuit;
The device is characterized in that it includes a switch means whose other end is grounded and which is turned on by an error detection signal.

Furthermore, a fourth aspect of the present invention is characterized in that, in the third aspect, the amount of increase in gain of the low frequency boost circuit is limited by the error detection signal.

"Operation" According to the first invention, if a disturbance such as vibration is applied to the CD player while the CD player is playing a CD, and the focus servo is disengaged and the read signal becomes below a predetermined voltage, a signal is output from the comparator. be done. As a result, the switch means is turned on in accordance with the output signal of the comparator. Therefore, the output signal of the phase compensation circuit is not supplied to the servo circuit, and the feed motor is stopped.

Further, according to the second invention, in the first invention, the amount of increase in the gain of the low frequency boost circuit is limited by the output signal of the comparator, and the number of track jumps of the optical pickup is reduced.

Further, according to the third invention, this CD player can play a CD
If a disturbance such as vibration is applied during reproduction of the image and the focus servo is deviated or a track jump occurs and an error detection signal is output, the switch means is turned on. Therefore, the output signal of the phase compensation circuit is not supplied to the servo circuit, and the feed motor is stopped.

Further, according to the fourth invention, in the third invention, the amount of increase in the gain of the low frequency boost circuit is limited by the error detection signal, and the number of track jumps of the optical pickup is reduced.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the first invention. In this diagram, parts corresponding to those in FIG. omitted.

In the servo circuit of the CD player shown in this figure, 23
and 24, a photosensor that converts the data reading laser beam reflected by the CDI into an electrical signal; 25 and 26, a current/voltage conversion circuit that converts the output current of the photosensors 23 and 24, respectively, into voltage;
27 is an RF signal generation circuit that generates an RF multiplied signal from the output voltages of the current/voltage conversion circuits 25 and 26.

This servo circuit also includes a comparator 28 that outputs an "H" level signal when the RF multiplied signal is below a predetermined level, and a resistor 29 between the phase compensation circuit 20 and the LPF 21.
A switch 30 is newly provided, one end of which is connected to the input terminal of the LPF 21, the other end of which is grounded, and which is turned on by the output signal of the comparator 2B.

In such a configuration, if the focus servo is disengaged due to disturbance such as vibration while the CD player is playing a CDI, the amount of light of the data reading laser beam incident on the photosensors 23 and 24 will decrease. Current/
The output voltages of the voltage conversion circuits 25 and 26 decrease, and the RF
When the double signal drops below a predetermined level, the comparator 23 outputs a signal at level . It is not supplied and the feed motor 4 stops.

In this way, if the focus servo is disengaged due to disturbances such as vibrations during CDI playback, the feed motor 4 is immediately stopped and the optical pickup 3 is
It will not run out of control to the inner or outer periphery of the DI and will not fall out of the data area of the CDI.

Next, an embodiment of the second invention will be described.

FIG. 2 is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the second invention. In this diagram, parts corresponding to those in FIG. Omitted. In the servo circuit of the CD player shown in this figure, the output signal of the comparator 28 is input to the low frequency boost circuit 19, and this signal reduces the amount by which the low frequency gain of the frequency characteristic of the tracking error signal is increased.

In such a configuration, if the focus servo is disengaged due to disturbance such as vibration while the CD player is playing a CDI, the amount of light of the data reading laser beam incident on the photosensors 23 and 24 will decrease. Current/
The output voltages of voltage conversion circuits 25 and 26 decrease, and IN
When the F signal falls below a predetermined level, the comparator 28
A @H' level signal is output from. Then, the switch 30 is turned on by the output signal of the comparator 28, and the amount of increase in the low-range gain of the frequency characteristic of the tracking error signal in the low-range boost circuit 19 is reduced. Then, the tracking error signal with the low-frequency gain lowered is input to the tracking driver 10 via the phase compensation circuit 20, and the tracking servo actuator I5 is driven. As a result, when the RF multiplied signal falls below a predetermined level, the tracking servo control signal is not supplied to the LPF 21, the feed motor 4 is stopped, and the amount of offset in the radial direction of the CDI of the objective lens of the optical pickup 3 is The number of track jumps will also decrease.

In this way, if the focus servo is disengaged due to disturbances such as vibrations during CDI playback, the feed motor 4 is immediately stopped and the optical pickup 3 is
It will not run out of control to the inner or outer periphery of the DI and will not fall out of the data area of the CDI. It also reduces the number of losses in track jumps.

In the above explanation, it is assumed that the tracking error signal is generated from two laser beams for tracking.
Although an embodiment of the so-called three-beam method has been shown, the servo circuit of the present invention can also be applied to the so-called one-beam method, in which a tracking error signal is generated from one laser beam for signal reading.

Next, an embodiment of the third invention will be described.

FIG. 3 is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the third invention. In this diagram, parts corresponding to those in FIG. Omitted. In the servo circuit of the CD player shown in this figure, 31 is a comparator for shaping the RF multiplied signal waveform, and 32 is a comparator 3! 33 is an input buffer; 34 is a slice level control circuit that controls the slice level of
35 is an LPF that passes the low frequency component of the output signal of the input buffer 33, and 35 is the output signal of the input buffer 33, that is,
The EFM demodulation circuit 6 that demodulates digital data from the EFM signal is a subcode demodulation circuit that demodulates subcodes such as the number of songs and time recorded in the CDI from the digital data.

In such a configuration, if a disturbance such as vibration occurs while the CD player is playing a CDI and the focus servo becomes disconnected or a track jump occurs,
In the CRC check of the subcode Q demodulated by the subcode demodulation circuit 36, an error occurs in the data.
An error detection signal is output from the subcode demodulation circuit 36. Then, the switch 30 is turned on by the error detection signal. As a result, the tracking servo control signal is not supplied to the LPF 21, and the feed motor 4 is stopped.

In this way, if a disturbance such as vibration is applied during CDI playback and the focus servo is disengaged or a track jump occurs, the feed motor 4 is immediately stopped and the optical pickup 3 is moved to the inner circumference of the CDI. Or, it will not run out of control to the outer periphery and fall out of the CDI data area. Next, an embodiment of the fourth invention will be described. FIG. 4 is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the fourth invention. In this figure, parts corresponding to those in FIG. Omitted. In the CD player shown in this figure, the error detection signal is input to the low frequency boost circuit 19, and this signal reduces the amount by which the gain in the low frequency range of the frequency characteristic of the tracking error signal is increased.

In such a configuration, if a disturbance such as vibration occurs while the CD player is playing a CDI and the focus servo becomes disconnected or a track jump occurs,
In the CRC check of the subcode Q demodulated by the subcode demodulation circuit 36, an error occurs in the data.
An error detection signal is output from the subcode demodulation circuit 36. Then, the switch 30 is turned on by the error detection signal, and the amount by which the low-frequency gain of the frequency characteristic of the tracking error signal is increased in the low-frequency boost circuit 19 is reduced. Then, the tracking error signal with the low-frequency gain lowered is input to the tracking driver IO via the phase compensation circuit 20, and the tracking servo actuator 15 is driven. This allows LPF
21 is not supplied with the tracking servo control signal, the feed motor 4 stops, and the optical pickup 3
The amount of offset in the radial direction of the CDI of the objective lens is also reduced, and the number of track jumps is reduced.

In this way, if a disturbance such as vibration is applied during CDI playback and the focus servo is disengaged or a track jump occurs, the feed motor 4 is immediately stopped, and the optical pickup 3/>4 CDI is It will not run out of control to the inner or outer circumference and fall out of the CDI data area.

Also, the number of track jumps is reduced.

The embodiment described above is a CD player for normal music reproduction, but the present invention is a CD-ROM.

CD-V (compact disc video), CD-I (
compact disc interactive media)
, LD (laser disc), and other playback devices.

[Effects of the Invention] As described above, according to the present invention, it is possible to prevent abnormal movement of the feed motor when a disturbance occurs, and there is an effect that it is possible to prevent runaway of the optical pickup.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the first invention, FIG. 2 is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the second invention, and FIG. The figure is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the third invention, FIG. 4 is a circuit diagram showing the configuration of a servo circuit of a CD player according to an embodiment of the fourth invention, and FIG. CDs according to the conventional example and an embodiment of the present invention
A block diagram showing the configuration of the player, Figure 6 is a conventional CD player.
FIG. 2 is a circuit diagram showing the configuration of a servo circuit of the player. 28...Comparator, -ta, 29...Resistor, 30...Switch.

Claims (4)

[Claims] (1) An optical pickup that reads data recorded on a disk, an amplifier that generates and outputs a tracking error signal from the read signal output from the optical pickup, and an amplifier that increases the gain of the low frequency component of the tracking error signal. a high frequency boost circuit, a phase compensation circuit that compensates for the phase of the output signal of the low frequency boost circuit, a feed motor that moves the optical pickup, and a low frequency component of the output signal of the phase compensation circuit that is used to move the feed motor. A comparator that outputs a signal when the read signal is lower than a predetermined voltage, one end of which is connected to the output terminal of the phase compensation circuit, and the other end of which is connected to the output terminal of the servo circuit. An optical disc player comprising: a resistor connected to an input terminal; and a switch means having one end connected to the input terminal of the servo circuit, the other end being grounded, and turned on by an output signal of the comparator. servo circuit. (2) The servo circuit for an optical disc player according to claim 1, wherein the amount of increase in gain of the low-frequency boost circuit is limited by the output signal of the comparator. (3) an optical pickup that reads data recorded on a disk; an amplifier that generates and outputs a tracking error signal from the read signal output from the optical pickup; and an amplifier that demodulates subcode data from the read signal and a demodulation circuit that detects errors in code data and outputs an error detection signal; and a low-frequency boost circuit that increases the gain of low frequency components of the tracking error signal.
a phase compensation circuit that compensates for the phase of the output signal of the low-frequency boost circuit; a feed motor that moves the optical pickup; and a servo circuit that drives the feed motor using a low frequency component of the output signal of the phase compensation circuit. an optical disc player comprising: a resistor having one end connected to the output terminal of the phase compensation circuit and the other end connected to the input terminal of the servo circuit; and a resistor having one end connected to the input terminal of the servo circuit; A servo circuit for an optical disc player, comprising a switch means whose end is grounded and which is turned on by the error detection signal. (4) The servo circuit for an optical disc player according to claim 3, wherein the gain increase amount of the low-frequency boost circuit is limited by the error detection signal.