JPH08249672A - Disk apparatus and method for adjusting offset of the disk apparatus - Google Patents

Abstract

PURPOSE: To correctly adjust offsets of various kinds at an optical disk player. CONSTITUTION: An objective lens 52 is moved to a lower end so as not to focus beams on a photodetector. An offset value of a focus servo error signal or the like is adjusted. When the objective lens 52 is moved to the lower end, influences of a returning light are eliminated, and therefore offsets can be adjusted while laser beams are emitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc device such as a compact disc or a mini disc, and more particularly to offset adjustment of a servo signal.

[0002]

2. Description of the Related Art In an optical disc player such as a compact disc player or a mini disc player, a focus servo circuit is provided to focus a laser beam from a pickup on the disc surface.
That is, the optical pickup of such an optical disc player is provided with, for example, a 4-division detector. A focus error signal is detected from the output of the 4-division detector. The objective lens is moved based on this focus error signal. As a result, the distance between the objective lens and the signal surface of the disc is constantly controlled, and the laser beam can always be focused on the disc surface even if the disc warps or the like.

The focus servo circuit is constructed, for example, as shown in FIG. That is, in FIG. 6, 101 is a 4-division detector. The four-divided detector 101 includes photodetectors 101A, 101B, 1
It is composed of 01C and 101D. The reflected light of the laser beam is condensed on the four-divided detector 101 via a cylindrical lens (not shown). The beam spot on the four-divided detector 101 becomes circular when the focus is just, and becomes elliptic when it shifts forward and backward.

The output of the photodetector 101A and 101
The output of C is added by the adder 102, and the output of the photodetector 101B and the output of 101C are added by the adder 103. The output of the adder 102 and the output of the adder 103 are subtracted by the subtractor 104. As described above, the beam spot on the four-divided detector 101 is circular when it is just focused and becomes elliptical when it is shifted back and forth, so that a focus error signal is obtained from the output of the subtractor 104.

As described above, as for the focus error signal, the output of the photodetector 101A and the output of 101C are added by the adder 102, the output of the photodetector 101B and the output of 101C are added by the adder 103, and the adder 1
It is obtained by subtracting the output of 02 and the output of the adder 103 by the subtractor 104. This focus error signal is
When there is no focus error, it should be "0" originally.

However, the focus error signal may not become "0" when there is no focus error because of variations in the gains and offsets of the operational amplifiers that form the adders 102, 103 and the subtractor 104. . Therefore, offset adjustment is performed at the time of factory shipment so that the focus error signal becomes "0" when there is no focus error. Incidentally, for example, in the case of using the power of the unbalance, when the power supply voltage and E _1, the focus error signal when the focus error is no example (E _1/2) V, and this (E _1/2) Offset adjustment is performed so that the error signal appears with V as the center value V _C.

That is, FIG. 7 shows a conventional focus servo circuit. In FIG. 7, the optical pickup 112 irradiates the disc 111 with a laser beam. The reflected light of this laser beam is detected by the optical pickup 112. The optical pickup 112 is provided with a four-division detector. The output of the optical pickup 112 is supplied to the focus error signal generation circuit 113. The focus error signal generation circuit 113 forms the focus error signal as described above. This focus error signal is supplied to the offset adder 114. An offset adder 114 adds an offset to the focus error signal. This offset adder 11
The output of No. 4 is supplied to the optical pickup 112 via the phase compensation circuit 115. As a result, the objective lens of the optical pickup 112 is moved up and down.

The offset adder 114 applies an offset voltage to the focus error signal so that the focus error signal becomes "0" when there is no focus error. This offset voltage is applied to the semi-fixed resistor 11
6 is set. The offset adjustment by the semi-fixed resistor 116 is manually performed at the time of factory shipment.

[0009]

However, if the offset adjustment is manually performed at the time of factory shipment, the adjustment work is troublesome and it is difficult to perform the optimum offset adjustment. In addition, the offset adjustment may go wrong due to changes over time. So, for example, when the power is turned on,
It is conceivable to automatically adjust the offset. When the offset adjustment is automatically performed as described above, it is considered necessary to turn off the laser beam so as not to be influenced by the returning light. When the laser beam is turned off, the output from the four-division detector does not appear, and the offset due to the operational amplifier that constitutes the adder or subtractor can be measured.

However, since the power consumption varies between when the laser beam is turned on and when the laser beam is turned off, the power supply voltage E ₁ changes.
For example using a power imbalance, if adjusted to the center value V _C is for example (E _1/2), when performing offset adjustment by Sho燈the laser beam, the change in the power supply voltage E _1, Center The level of the value V _C fluctuates, and correct offset adjustment cannot be performed. Therefore, when adjusting the offset, it is necessary to turn on the laser beam. However, if the laser beam is turned on to perform the offset adjustment, a signal appears in the photodetector due to the influence of the returning light of the disk, and the correct offset adjustment cannot be performed.

Therefore, an object of the present invention is to provide a disk device which can correctly perform various offset adjustments while a laser beam is lit.

[0012]

According to the present invention, there is provided a pickup means for irradiating a disk with light and detecting reflected light from the disk, and an objective lens for condensing the light from the optical pickup means on the disk. The position of the objective lens is adjustable by a control signal, and a bias signal is provided to the servo error signal so as to compensate the offset value of the servo error signal and the signal forming means that forms the servo error signal from the output of the pickup. A disc device having a bias signal adding means and adapted to set the position of the objective lens with respect to the disc to a position not in focus when adjusting the offset value of the servo error signal.

[0013]

The objective lens is positioned at the lower end when adjusting the offset value of the servo error signal. As a result, even when the offset adjustment is performed while the laser beam is being irradiated, the influence of the return light is eliminated.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The present invention is applied to, for example, a mini disc player that records / reproduces a digital audio signal on a disc (mini disc) having a diameter of 64 mm housed in a cartridge.

FIG. 1 shows an embodiment of a mini disc player to which the present invention is applied. In FIG. 1, reference numeral 1 is a disc. The disc 1 includes a reproduction-only disc and a recording / reproduction disc. The disk 1 is rotationally driven by a spindle motor 2.

An optical head 3 is provided for the disk 1. The optical head 3 is provided with a laser diode for irradiating a laser beam, an optical system including a polarization beam splitter, an objective lens 3A, and the like, a detector for detecting reflected light from the disk 1, and the like. The objective lens 3A can be moved by the biaxial device 4 in the disc radial direction (tracking direction) and in the direction of approaching and leaving the disc (focusing direction).

That is, FIG. 2 is an example of a biaxial device. As shown in FIG. 2, the biaxial device 51 is provided with an objective lens 52, an FCK coil 53, and a TCK.
An RK coil 54 is provided. The FCK coil 53 moves the objective lens 52 in the focus direction as shown by an arrow A1. The TRK coil 54 moves the objective lens 52 in the tracking direction as indicated by arrow B1. Focus servo and tracking servo are operated by passing a control current to the FCK coil 53 and the TRK coil 54 based on the focus error signal and the tracking error signal.

In FIG. 1, the laser beam from the laser diode of the optical head 3 has a high level at the time of recording because it heats the recording track to the Curie temperature, and at the time of reproduction, from the pit data or the reflected light due to the magnetic Kerr effect. Relatively low level to detect data.

6A is a magnetic head. Magnetic head 6A
Are arranged to face the optical head 3. Magnetic head 6
A applies a magnetic field modulated by data to the disk 1 during recording. The entire optical head 3 and the magnetic head 6A can be integrally moved in the radial direction of the disk by the sled mechanism 5.

Reference numeral 7 is an RF amplifier, and the RF amplifier 7 is
From the output of the detector of the optical head 3, a reproduction RF signal, a tracking error signal, a focus error signal, etc. are extracted by arithmetic processing. The output of the RF amplifier 7 is supplied to the digital servo circuit 9.

That is, as shown in FIG. 3, the photodetectors 61A to 61E are arranged in the optical pickup 4. The just focus, 4 beam spot focused on the split detector 61A~61D becomes circular, deviates back and forth, since the elliptical, output S _A of the photodetector 61A, S _B the output of the photo disk motor 61B, Assuming that the output of the photodetector 61C is S _C and the output of the photodetector 61D is S _D , the focus error signal is obtained by the calculation of (S _A + S _C ) − (S _B + S _D ).
If there is no tracking error, the beam comes to the center of the photodetectors 61A to 61D, so the output of the photodetector 61E is S _E , and the photodetector 61F
When the output of S is S _F , the tracking error signal is obtained by the calculation of (S _E −S _F ). Further, a reproduction RF signal can be obtained by (S _A + S _C + S _B + S _D ).

The digital servo circuit 9 is supplied with a tracking error signal, a focus error signal and an RF signal from the RF amplifier 7. Further, the digital servo circuit 9 is provided with a track jump command, an access command, rotation speed detection information of the spindle motor 2 and the like from the system controller 11. In response to this, various servo drive signals are sent from the digital servo circuit 9 to the PW, for example.
It is generated in the form of M signals. The output of the digital servo circuit 9 is supplied to the servo driver 8. The biaxial mechanism 4 and the sled mechanism 5 are driven by the output of the servo driver 8 to perform focus and tracking control.

Further, the servo driver 8 applies power corresponding to the PWM signal as the spindle error signal to the motor driver 13. The motor driver 13 is a so-called three-phase switching drive motor. During normal recording / reproduction, the rotation speed information of the spindle motor 2 is obtained from the reproduction data. That is, in the digital servo circuit 9, the reproduction clock is extracted from the edge detection of the reproduction RF signal (EFM signal), and compared with the reference clock to generate the spindle error signal. Based on such a spindle error signal, the spindle motor 2 is controlled to a constant speed (CLV).

Reference numeral 10 is a signal processor. Signal processing unit 10
Is composed of an encoder / decoder unit 10A, a memory control unit 10B, and an encoder / decoder unit 10C. The signal processing unit 10 uses an encoder /
The decoder unit 10C compresses the digital audio signal and temporarily stores it in the buffer RAM 12. Then, the encoder / decoder unit 10A performs error correction coding processing and EM
F-modulate and output. At the time of reproduction, the encoder / decoder unit 10A performs error correction processing and EMF demodulation, and temporarily stores this data in the buffer RAM 12. And
The encoder / decoder unit 10C decompresses and outputs.

Reference numeral 14 is a converter, which is a D / A converter 14
An A / A / D converter 14B is provided. The digital audio data output by the audio compression decoding processing of the encoder / decoder unit 10C is converted into an analog signal by the D / A converter 14A, output from the line output terminal 15, and output as, for example, an LR audio signal. Alternatively, it is supplied to the headphone output terminal 18 via the electronic volume 16 and the headphone amplifier 17.

At the time of reproduction, address information, subcode data and the like are extracted by the encoder / decoder section 10A and supplied to the system controller 11. These pieces of information are used for various control operations.

When the headphone to be connected is provided with a remote commander, the signal from the remote commander is placed at the same position as the headphone output terminal 17, for example, a remote control input / output terminal 19 in the form of a 4-terminal connector.
Is supplied to the system controller 11. When the remote commander has a display unit, the system controller 11 sends a display control signal to the remote control input / output terminal 1
It will be output from 9.

Reference numeral 25 denotes a display unit, and the display unit 25 is composed of, for example, a liquid crystal display. Display unit 2
5, based on the control of the system controller 11,
The operating status, track number, time information, character information, etc. are displayed.

Reference numeral 26 denotes an operation unit provided with keys for user operation, including a reproduction key, a recording key, a stop key, and an A key.
An MS key, a search key, etc. are provided so as to be operated by the user.

Reference numeral 27 is a stepper driver, and 28 is a stepper motor, which is a driving portion for raising and lowering the magnetic head 6A. This operation is controlled by the system controller 11.

Reference numeral 29 denotes an EEPROM, which holds various servo coefficients in the digital servo system, for example. The system controller 11 is an EEPROM 29
Then, the required coefficient is extracted from and is supplied to the digital servo circuit 9. The system controller 11
The RAM 11A shown inside is a work area in the system controller 11.

Reference numeral 30 denotes a clock unit, which constantly counts the year, month, day, hour, minute, and second by a small battery different from an operating power source and the like, so that the system controller 11 can always discriminate the current date and time.

Reference numeral 31 is a power supply circuit for supplying an operating power supply to each part. In addition to using a battery 33 housed as a power supply, a commercial power supply can be used by connecting an AC adapter to the DC-IN terminal 32.

The power supply voltage from the power supply circuit 31 is supplied to the system controller 11 via the microcomputer power supply circuit 35. Further, the DC / DC co-inverter 34 outputs the operating power supply voltage to each unit.

At the time of recording, an audio signal is supplied from the optical / line input terminal 20 or the microphone input terminal 21. An analog audio signal from the optical / line input terminal 20 or an audio signal input from the microphone input terminal 21 and amplified by the microphone amplifier 22 is sent to the A / D converter 14B via the AGC circuit 23 and the electronic volume 24. Supplied. A /
The D converter 14B converts the analog audio signal into digital audio data in the form of 16-bit quantization and 44.1 kHz sampling. Then, it is supplied to the encoder / decoder unit 10C and subjected to audio compression encoding processing. The digital audio signal from the optical / line input terminal 20 is directly supplied to the encoder / decoder section 10C.

The recording data compressed by the encoder / decoder section 10C is once written in the buffer RAM 12 by the memory control 10B and is read out at a predetermined timing, and the encoder / decoder section 10C is read.
After being subjected to encoding processing such as CIRC encoding and EFM modulation at A, it is supplied to the magnetic head drive circuit 6 via the digital servo circuit 9.

The magnetic head drive circuit 6 supplies a magnetic head drive signal to the magnetic head 6A according to the encoded recording data. That is, an N or S magnetic field is applied to the disk 1 by the magnetic head 6. Also,
At this time, the system controller 11 outputs a recording level laser beam to the optical head.
Control the laser power. Further, during recording, the digital servo circuit 9 performs position servo with respect to the magnetic head 6A to keep the relative distance between the magnetic head 6A and the disk 1 substantially constant. Further, during recording, the spindle servo compares the clock obtained from the groove on the disk 1 with the reference clock to generate a servo error signal, and performs CLV control.

During reproduction, the optical head 3 intermittently reads information from the disc 1. This reproduction information is supplied to the RF amplifier 7. The reproduced RF signal from the RF amplifier 7 is supplied to the encoder / decoder unit 10A and subjected to processing such as EFM demodulation, CIRC processing, and CD-ROM decoding. Then, the memory control unit 1
It is once written in the buffer RAM 12 by 0B.
The data written in the buffer RAM 12 is supplied to the encoder / decoder unit 10C. Then, reproduction signal processing such as decoding processing for audio compression processing is performed,
Digital audio data in the form of 16-bit quantization and 44.1 KHz sampling. This voice data is
The analog signal is returned to the analog signal by the D / A converter 14A, output from the line output terminal 15, and output as, for example, an LR audio signal. Alternatively, it is supplied to the headphone output terminal 18 via the electronic volume 16 and the headphone amplifier 17.

When the recording / reproducing operation is performed on the disc 1, the management information recorded on the disc 1, that is,
It is necessary to read the P-TOC and U-TOC. That is, when the disc is mounted, the optical pickup 4 is moved to the lead-in areas 51A and 51B at the innermost periphery, and P-
The management information is read from the TOC. If the loaded disc is the recording / reproducing disc 1B, U
-Management information is read from the TOC area. The system controller 11 determines the address of the area to be recorded on the disc 1 and the address of the area to be reproduced according to the management information.

When recording is performed on the recording / reproducing disc 1B, the information of the U-TOC is edited according to the recording or erasing of data each time recording / erasing is performed.
The information is moved to the -TOC area 54 and the U-TOC information is rewritten. When the eject operation of the disc 1 is performed or the power off operation is performed, the UT
The operation is stopped after the OC is rewritten.

As described above, in such a recording / reproducing apparatus, as shown in FIG.
~ 61F is placed in the optical pickup 3, and (S _A + S
_The focus error signal is obtained by the calculation of ( _C ) − (S _B + S _D ), the tracking error signal is obtained by the calculation of (S _E −S _F ), and the focus error signal is obtained by (S _A + S _C + S _B + S).
_The reproduction RF signal is obtained by the calculation of _D ).

FIG. 4 shows a specific structure of the RF amplifier 7 in the recording / reproducing apparatus to which the present invention is applied.
The RF amplifier 7 includes photo detectors 61A to 61F.
Operational amplifiers 71A to 71F for converting the output of the I-V to
(S _A + S _C) - and (S _B + S _D) comprising an operational amplifier 72 for performing an operation, and _{(S A + S C + S} B + S D) becomes operational performs an operational amplifier 73, comprising (S _E -S _F) operation And an operational amplifier 75 for performing. Further, in the recording / reproducing apparatus to which the present invention is applied, an unbalanced power source is used, and the center value of the error voltage is set to V _C. Therefore, an operational amplifier 75 is provided to generate this center value V _C. Further, an operational amplifier 76 is provided for applying a bias so that the center value of the focus error signal becomes V _C.

That is, the output of the photodetector 61A is IV converted by the operational amplifier 71A, and the operational amplifier 7
2 and the operational amplifier 73.
It is supplied to the inverting input terminal of. Photo detector 61B
The output of is converted to IV by the operational amplifier 71B and supplied to the non-inverting input terminal of the operational amplifier 72 and the inverting input terminal of the operational amplifier 73. The output of the photodetector 61C is IV converted by the operational amplifier 71C and supplied to the inverting input terminal of the operational amplifier 72 and the inverting input terminal of the operational amplifier 73. The output of the photo detector 61D is I-
It is V-converted, supplied to the non-inverting input terminal of the operational amplifier 72, and supplied to the inverting input terminal of the operational amplifier 73.

In the operational amplifier 72, the added value of the operational amplifiers 71A and 71C is subtracted from the added value of the operational amplifiers 71B and 71D. A focus error signal is obtained from the output of the operational amplifier 72. The output of the operational amplifier 72 is supplied to the inverting input terminal of the operational amplifier 76. A bias value for offset compensation is given as a PWM signal from the system controller 11, and the PWM signal is supplied to the operational amplifier 76 via the low-pass filter 77. The operational amplifier 76 adds the offset value to the focus error signal.

In the operational amplifier 73, operational amplifiers 71A to 71A
The 1D outputs are added. An RF signal is obtained from the output of the operational amplifier 73.

The output of the photodetector 61E is IV converted by the operational amplifier 71E and supplied to the non-inverting input terminal of the operational amplifier 74. The output of the photo detector 61F is IV converted by the operational amplifier 71F, and the operational amplifier 7F
4 is supplied to the inverting input terminal. The operational amplifier 74 subtracts the output of the operational amplifier 71E from the output of the operational amplifier 71F. The tracking error value is output from the output of the operational amplifier 74.

A center value obtained by dividing the power supply voltage E ₁ is applied to the operational amplifier 75. As a result, the center value V _C is formed.

On the digital servo circuit 9 side, the levels of the tracking error signal, the RF signal, the tracking error signal, and the center value thus obtained are A /
D converted. Then, the tracking error signal, RF
The signal and the tracking error signal are subtracted from the center value.

That is, the center value V _C from the operational amplifier 75 is digitized by the A / D converter 84. Then, an average value circuit 85 to 87 calculates an average value of the center value V _C , and the average value of the center values is subtracted from the subtracters 89 to 9
1 is supplied. The focus error value from the operational amplifier 76 is digitized by the A / D converter 81 and supplied to the subtraction circuit 89. The RF signal from the operational amplifier 73 is digitized by the A / D converter 82 and supplied to the subtractor 90. The output of the subtractor 90 is further supplied to the subtractor 92. The tracking error signal from the operational amplifier 75 is digitized by the A / D converter 83 and supplied to the subtractor 91.

With such a configuration, when there is no focus error, the center value of the focus error signal from the subtractor 89 should be V _C. However, this may not occur due to the offset voltage of the operational amplifier 72 or the like. Therefore, in one embodiment of the present invention, offset adjustment is performed, for example, when the power is turned on so that the center value of the focus error becomes V _C. When making such an adjustment, processing as shown in FIG. 5 is performed.

It is determined whether the power is turned on (step S1). When the power is turned on, the optical pickup 3
Objective lens 52 is lowered to the lowest end (step S
2). Then, a laser beam is emitted from the optical pickup 3 (step S3). In this way, when the objective lens 52 is lowered, the object is not in focus. Therefore, even if the laser beam is irradiated, the photodetectors 61A to 61A to
There is no effect of returning light on 61F. In this state,
Offset adjustment is performed (step S4). When the offset adjustment is performed, the position of the objective lens 52 is returned (step S5).

As described above, in the embodiment of the present invention, since the offset adjustment is performed with the objective lens 52 lowered, even when the laser beam is irradiated, the influence of the returning light is influenced by the photodetectors 61A to 61F. The offset adjustment can be performed while the laser beam is being irradiated.

For the RF signal, similarly, the level when there is no signal is averaged and the averaged level is given to the subtractor 92 for adjustment. Also in this case, similarly, the offset adjustment is performed in the state where the objective lens 52 is lowered, so that the adjustment is performed in the state in which the laser beam is emitted.

Further, in this embodiment, the focus error offset adjustment is performed by the balance adjustment resistor 93, and automatic adjustment at power-on is not performed. Adjustment can be performed in the same manner.

[0055]

According to the present invention, the objective lens is positioned at the lower end when adjusting the offset value of the servo error signal. As a result, even when the offset adjustment is performed while the laser beam is being irradiated, the influence of the reflected light is eliminated. Therefore, even if the laser beam is turned on and the offset is adjusted with the disc still mounted, the offset value can be adjusted correctly without being affected by the returning light.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of an optical disc recording / reproducing apparatus to which the present invention is applied.

FIG. 2 is an exploded perspective view used to describe an example of a biaxial device.

FIG. 3 is a plan view used to describe an example of an optical detector.

FIG. 4 is an RF in an optical disc to which the present invention is applied.
It is a connection diagram used for the description of the circuit.

FIG. 5 is a flow chart used for explaining one embodiment of the present invention.

FIG. 6 is a schematic diagram used to describe a conventional focus servo circuit.

FIG. 7 is a block diagram used to describe a conventional focus servo circuit.

[Explanation of reference numerals] 1 disk 7 RF amplifier 11 system controller

Claims (3)

[Claims] 1. A pickup means for irradiating a disc with light and detecting reflected light from the disc, an objective lens for converging light from the optical pickup means onto the disc, and an objective lens for the objective lens. The position is adjustable by a control signal, and a signal forming means for forming a servo error signal from the output of the pickup, and a bias for giving a bias signal to the servo error signal so as to compensate the offset value of the servo error signal. And a signal adding means, when adjusting the offset value of the servo error signal,
A disc device in which the position of the objective lens with respect to the disc is set to a non-focus position. 2. The disk device according to claim 1, wherein the non-focus position is a position where the objective lens is moved to a lower end. 3. An offset adjusting method for a disk device, wherein, when adjusting the offset value of the servo error signal, the position of the objective lens with respect to the disk is set to a non-focus position and the disk is irradiated with light. .