JPH06267094A - Optical disc apparatus - Google Patents

Abstract

PURPOSE:To correct a tracking error signal thereby to carry out controlling with the tracking error signal not including a direct current offset even when the total amount of the returning light from a disc is changed due to the insufficient adjustment of an optical system or the like. CONSTITUTION:An oscillation signal of an oscillator 12 drives a tracking actuator 16 via a changing switch 13 and a drive circuit 15 at the adjusting time. A position sensor 10 detects the shifting amount of an objective lens by the tracking actuator 16, and an offset detecting/correcting circuit 11 stores an offset value corresponding to the shifting amount. During the normal operation, a correction corresponding to the output from the position sensor 10 is conducted by the offset detecting/correcting circuit 11, so that the tracking actuator 16 is driven without being shifted via a phase compensation circuit 14, the changing switch 13, the drive circuit 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for performing tracking control in which a beam applied to an optical disk through an objective lens is made to follow a recording track.

[0002]

2. Description of the Related Art FIG. 11 shows an example of an optical disk device which employs a push-pull method for a single beam tracking servo. In the configuration of FIG. 11, the laser light emitted from the laser diode 20 is applied to the disk 24 via the collimator lens 21, the beam splitter 22, and the objective lens 23. The return light reflected by the disc 24 is the objective lens 23 and the beam splitter 2.
2. The light is focused on the split photodetector 26 through the multi-lens 25 including a cylindrical lens and a condenser lens. The divided photodetector 26 outputs each output photoelectrically converted from the divided photodetector 26 to the head amplifier 27. The head amplifier 27 is
Each output is amplified and output to the matrix amplifier 28.

The matrix amplifier 28 performs addition and subtraction of the supplied outputs to output a focus error signal, a tracking error signal and an RF signal, respectively. The focus error signal and the tracking error signal pass through the phase compensation circuits 29 and 14 and drive circuit 30,
15 are supplied respectively. Drive circuit 30, 15
Is the focus actuator 3 based on the supplied focus error signal and tracking error signal.
1. The objective lens 23 is controlled to move by driving the tracking actuator 16.

In the tracking control adopted by this optical disk apparatus, when the objective lens 23 moves in the radial direction of the disk 24, the beam spot on the split photodetector 26 also moves. This beam spot is the split photodetector 26.
When moved up, the multi-amplifier 28 generates a tracking error signal including an offset component in the output signal.

Therefore, the optical disk device is equipped with a position sensor 10 for detecting the position of the objective lens 23 in the disk radial direction as schematically shown in FIG. 11, and the output of the position sensor 10 is supplied to a phase compensation circuit 40 and a drive circuit. It is applied to the sled actuator 42 through 41. The sled actuator 42 applies a signal to correct a position according to a fixed adjustment value set at the time of factory shipment, for example, and applies a sled servo so that the objective lens 23 does not move largely.

[0006]

By the way, in the above-mentioned optical disk apparatus, the main reason for the large position movement of the objective lens in the radial direction of the disk is the eccentricity of the disk. When an attempt is made to follow the sled servo in order to cancel this eccentricity, the compensating operation for the movement of the objective lens can be easily followed even if the rotational speed of the disk is low.

However, when the number of rotations of the disk increases beyond a certain range, it becomes difficult to follow the compensation operation with respect to the movement of the objective lens. In order to solve this problem, it is generally attempted to deal with the problem by using parts having good followability even at high-speed rotation of the disk. In general, the optical disk device consumes more power and generates more heat, and the cost of the device itself increases. I will end up.

Further, since the optical disk device cannot apply the thread servo as described above during the seek operation, the tracking error signal is offset due to the shaking of the objective lens. For this reason, the optical disk device can apply the tracking servo only after a certain period of time as a settling time has elapsed after the movement of the sled accompanying the seek operation.

Therefore, the present invention has been made in view of the above-mentioned circumstances, and for example, even if the total amount of light returned from the disc changes due to insufficient adjustment of the optical system or the like, a tracking error signal is generated. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disc device capable of correcting the error to obtain a tracking error signal that does not include a DC offset.

[0010]

An optical disk apparatus according to the present invention detects a displacement amount of the objective lens in an optical disk apparatus which performs tracking control to cause a beam irradiated on the optical disk through an objective lens to follow a recording track. And a tracking error signal obtained during normal operation by detecting the offset included in the tracking error signal in accordance with the detection signal from the displacement amount detecting means and holding the detected offset during offset adjustment. The above problem is solved by having an offset detection and correction means for correcting the offset amount.

Here, the tracking control is performed by a push-pull method. The offset detection correction means is
Offset detection means for detecting an offset included in the input tracking error signal, oscillation means for outputting an oscillation signal for vibrating the objective lens in the radial direction of the optical disc, and offset according to the output of the displacement amount detection means. A look-up table that outputs a cancel voltage, an adder that adds an output signal from the look-up table and a tracking error signal that is input, an oscillation signal from the oscillator, and an output signal from the adder And switching means for switching, and control means for supplying the output from the offset detecting means to the look-up table in correspondence with the switching control of the switching means and the output of the displacement amount detecting means to perform data rewriting control. It consists of.

Next, the offset detecting / correcting means outputs an oscillating signal for oscillating the objective lens in the radial direction of the optical disc, and an offset detecting the presence / absence of an offset included in the tracking error signal supplied. Zero detection means, a look-up table that outputs an offset cancel voltage according to the output of the displacement amount detection means, an addition means that adds an output signal from the look-up table and a tracking error signal that is input, Switching means for switching the oscillation signal from the oscillating means and the output signal from the adding means, the switching control of the switching means, and the look-up according to the output of the displacement amount detecting means and the output result of the offset zero detecting means. It is composed of a control means that controls rewriting of the offset value output from the table. To set canceled.

Further, the offset detection / correction means is
Offset detection means for detecting an offset included in the input tracking error signal, oscillation means for outputting an oscillation signal for vibrating the objective lens in the radial direction of the optical disc, and the offset for the displacement amount of the displacement amount detection means. The slope obtained from the offset of the detecting means is supplied as a multiplier, and the multiplying means for multiplying the multiplier and the displacement amount to output the offset value and the output from the multiplying means and the input tracking error signal are added. Adding means, switching means for switching the oscillation signal from the oscillating means and the output signal from the adding means, the switching control of the switching means, and the offset of the offset detecting means with respect to the displacement amount of the displacement amount detecting means. It may be configured with a control unit that calculates a multiplier and controls the supply to the multiplication unit.

[0014]

In the optical disk device according to the present invention, when tracking control is performed so that the beam irradiated onto the optical disk through the objective lens follows the recording track, the displacement amount detecting means detects the displacement amount of the objective lens and the offset detection correction is performed. The offset value detected at the time of the offset adjustment and the displacement amount of the objective lens are set in association with each other by using the means, and the offset detection correction means according to the setting is set according to the setting during the normal operation. The offset amount is corrected to improve the tracking servo when reading or writing the optical disk device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the principle structure of the main block of the optical disk device in this embodiment. here,
The optical disk device of the present embodiment will be described by taking the case of using the push-pull method using a single beam as an example.

The structure shown in FIG. 1 has a position as a displacement amount detecting means for detecting the displacement amount of the objective lens in an optical disc device for performing tracking control in which a beam emitted to the optical disc through an objective lens is made to follow a recording track. The offset included in the tracking error signal is detected according to the sensor 10 and the detection signal from the position sensor 10, and the detected offset is held during offset adjustment to obtain the offset amount of the tracking error signal obtained during normal operation. It has an offset adjustment unit 1 as an offset detection correction unit for correction.

The offset adjusting section 1 includes an offset detecting / correcting circuit 11, an oscillator 12 and a changeover switch 13.
It consists of and.

The tracking error signal including the offset component supplied via the input terminal 17 of FIG. 1 is offset by the offset detection / correction circuit 11 and is sent to the phase compensation circuit 14. The phase compensation circuit 14
The tracking error signal including no offset is phase-compensated and supplied to the drive circuit 15 via the changeover switch 13. The drive circuit 15 drives the tracking actuator 16 to move the objective lens. At this time, the tracking actuator 16 corrects the movement of the objective lens of the optical disc device by performing tracking control by driving the objective lens with a tracking error signal having no offset.

A first embodiment of the offset adjusting section 1 in the optical disk device will be described with reference to the block diagram shown in FIG. Here, common parts are given the same reference numerals. The offset adjustment unit 1 in FIG. 2 includes a lookup table 11a, a CPU 11b, an offset detection circuit 11c, an adder 11d, an oscillator 12, and a changeover switch 13.

The offset adjusting section 1 applies a predetermined vibration to the objective lens in advance, and performs an operation of associating the movement of the objective lens at this time with the offset included in the tracking error signal in the offset adjusting mode. Therefore,
This offset adjustment mode is a mode for performing a calibration operation for canceling the offset included in the tracking error signal.

In this offset adjustment mode, the oscillator 1
Reference numeral 2 is used as an oscillating means for outputting an oscillating signal for vibrating the objective lens in the radial direction of the optical disc. The oscillator 12 supplies the oscillation signal to the drive circuit 15 via the terminal a of the changeover switch 13. The drive circuit 15 supplies a drive signal to the tracking actuator 16. Tracking actuator 16
Moves the objective lens in the radial direction of the optical disc. Since the movement of this objective lens appears as an offset,
The position sensor 10 detects the movement of the objective lens by the oscillation signal of the oscillator 12 in this mode. The position sensor 10 uses the detection signal as a lookup table 11a.
And CPU 11b.

The look-up table 11a receives the output of the position sensor 10 as address data, writes the output of the offset detection circuit 11c as an offset value corresponding to the address data, and responds to the input of the address data during normal operation. Corresponds to a displacement correction output means for outputting an offset value as an offset cancel voltage. The structure of the lookup table 11a is described in detail later.

The CPU 11b controls the changeover of the changeover switch 13 and the position sensor 1 as described later.
The output from the offset detection circuit 11c is supplied to the look-up table 11a in correspondence with the output of 0, and is used as control means for performing data rewriting control. The tracking error signal is supplied to the offset detection circuit 11c and the adder 11d via the input terminal 17. The offset detection circuit 11c is provided as offset detection means for detecting the offset included in the input tracking error signal.

In this way, the lookup table 11a
Is the position sensor 10 that is associated with the movement of the objective lens in advance.
Is used as address data, and the offset detection circuit 11
The CPU 11b is controlled to hold the offset value detected in c as data for the address.

Position sensor 10 during normal operation
Supplies the detection signal to the lookup table 11a. The look-up table 11a adds the offset cancel voltage corresponding to the supplied detection signal to the adder 11d.
Output to. The adder 11d inputs the output signal from the lookup table 11a, for example, to one end side,
The tracking error signal input to the other end is added and input, and the offset of the tracking error signal output is canceled. Here, if the offset output from the lookup table 11a is supplied with the same sign as the output signal of the offset detection circuit 11c, the adder 11d makes the input on the one end side a subtraction input.

This adder 11d outputs the offset canceled tracking error signal to the phase compensation circuit 14. The phase compensation circuit 14 performs phase compensation of the tracking error signal and supplies it to the terminal b of the changeover switch 13.

The changeover switch 13 is used as a changeover means for changing over the oscillation signal from the oscillator 12 and the output signal from the adder 11d. Changeover switch 13
Supplies the phase-compensated offset canceled tracking error signal to the drive circuit 15. The drive circuit 15 outputs a drive signal from the tracking error signal to the tracking actuator 16. The tracking actuator 16 holds the objective lens at a predetermined position.

The operation of each part will be further described. C
The PU 11b takes in the value of the displacement amount and the value of the offset amount, respectively, and controls the lookup table 11a.
The CPU 11b controls to store in the lookup table 11a a value that is equal to the absolute value of the supplied offset amount and has the opposite polarity while associating with the output value of the position sensor 10 supplied to the lookup table 11a. Is going. By performing the above-described operation, the offset cancel value of this optical disk device is created in the lookup table.

Next, in response to the switching from the offset adjustment mode to the normal operation mode, the changeover switch 13 changes the terminal b.
Is switched to the side. The offset detection circuit 11c detects an offset included in the tracking error signal supplied through the input terminal 17 during the normal operation. C
The PU 11b outputs the value stored to cancel the offset amount value as a voltage to the adder 11d. The adder 11d adds a tracking error signal including an offset and an offset cancel output of the opposite polarity, which is equal in magnitude to the offset. Adder 11d
Supplies the tracking error signal not including the offset amount to the phase compensation circuit 14. The phase compensation circuit 14 supplies the phase-compensated tracking error signal to the drive circuit 15 via the changeover switch 13. The drive circuit 15 drives the tracking actuator 16 to cancel the displacement of the objective lens.

Here, the offset detection circuit 11c will be described with reference to the circuit diagram of one specific example shown in FIG. The tracking error signal is sent to the peak hold circuit 111 and the bottom hold circuit 11 via the input terminal 17.
2 is supplied. The peak hold circuit 111 supplies the tracking error signal to the non-inverting terminal of the comparison amplifier 111a. The comparison amplifier 111a outputs the diode D
No. 1 is supplied to the anode side. The diode D1 outputs the output signal to the comparison amplifier 1 via one end of the capacitor C1.
It is supplied to the non-inverting terminal of 11b. Above capacitor C
The other end side of 1 is grounded. The comparison amplifier 111b feeds back the output to the inverting terminal, and
It is also input to the inversion terminal of.

Further, the bottom hold circuit 112 inputs the supplied tracking error signal to the inverting terminal side of the comparison amplifier 112a via the resistor R1. The non-inverting terminal side of the comparison amplifier 112a is grounded. The comparison amplifier 112a supplies the output to the inverting terminal side of the comparison amplifier 112a via the feedback resistor R2, and the comparison amplifier 1
A signal is output to the non-inverting terminal side of 12b. The bottom hold circuit 112 supplies the output signal from the comparison amplifier 112a to the circuit configured by the comparison amplifiers 112b and 112c, the diode D2, and the capacitor C2. The circuit configured by the comparison amplifiers 112b and 112c, the diode D2 and the capacitor C2 has the same connection configuration as the peak hold circuit 111 described above. Comparison amplifier 11
3a supplies the output signal to the non-inverting terminal via the resistor R3. The comparison amplifier 113a has a resistor R5 at its inverting terminal.
The output signal from the peak hold circuit 111 is input via. The comparison amplifier 113a outputs the feedback resistance R
A bias voltage −V for input to the inverting terminal and an A / D converter 114, which will be described later, is fed back to the inverting terminal via 6 through one end of the resistor R7. The comparison amplifier 113 acts as a subtractor and supplies the offset level to the A / D converter 114. The A / D converter 114 converts the level of the detected offset into a digital value and C
It is output to the PU 11b.

With such a configuration, the offset adjustment mode is performed, for example, when the optical disc is replaced, or when the spindle motor reaches a certain rotation speed during spin-up, and is supplied in the normal operation mode. The offset of the tracking error signal generated can be canceled.

Next, a second embodiment of the offset adjusting section 1 in the optical disk device will be described with reference to the block diagram shown in FIG. Here, common parts are given the same reference numerals, and description thereof is omitted. The offset adjusting unit 1 of FIG. 4 also has a lookup table 11a, a CPU 11b, an adder 11c, an oscillator 12 and a changeover switch 13 as in the first embodiment.

The offset adjusting section 1 is provided with an offset zero detecting circuit 11e instead of the offset detecting circuit 11c shown in FIG. The offset zero detection circuit 11e is offset zero detection means for detecting the presence or absence of an offset included in the input tracking error signal. The offset zero detection circuit 11e will be described in detail later with reference to the circuit diagram.

The operation of the offset adjusting section 1 in the second embodiment will be described with reference to FIG. The changeover switch 13 switches to the terminal a side in the offset adjustment mode. Oscillator 1 in this offset adjustment mode
2 supplies the output to the drive circuit via the changeover switch 13. In this oscillator 12, an objective lens (not shown) by a tracking actuator 16 according to the output of the oscillator 12 is vibrated in the radial direction of the optical disc according to the oscillation amplitude. Tracking actuator 16
The displacement of the objective lens due to
The value corresponding to the displacement amount is detected with. Position sensor 1
0 uses this value as lookup table 11a and CPU1
And 1b.

Further, the adder 11d supplies an output obtained by adding the tracking error signal supplied through the input terminal 17 and the offset canceling output from the look-up table 11a to the phase compensating circuit 14 and at the same time, performs offsetting. It is supplied to the zero detection circuit 1e. The offset zero detection circuit 11e detects the presence / absence of an offset included in the tracking error signal, and supplies, for example, a combined output of "0", "+", "-" to the CPU 11b as a value indicating the presence / absence of this offset. To do.

The CPU 11b controls the rewriting of the offset value output from the lookup table 11a by taking in the value of the displacement amount and the value indicating the presence or absence of the offset, respectively. The CPU 11b associates the output value of the position sensor 10 supplied to the look-up table 11a with the output value from the offset zero detection circuit 11e and indicates that the value is, for example, “0”, which is an appropriate offset cancel value. The control is repeated until it is supplied. In this control, the output voltage, which is output from the offset zero detection circuit 11e and whose offset value is increased (or decreased) at a constant level according to the control of the CPU 11b, is output to the adder 11d.

By repeating this operation, the CPU 11b
When the offset zero detection circuit 11e outputs the value "0", the displacement amount of the position sensor 10 is used as address data and the voltage output from the lookup table 11a is used as an offset cancel voltage to store digital data corresponding to this voltage. At this time, the look-up table 11a has the absolute value of the offset equal to the magnitude under the control of the CPU 11b, and stores the value of the opposite polarity as the data for offset cancellation. By performing the above-described operation, the CPU 11b controls the offset cancel value of the optical disk device to create the lookup table 11a and rewrite the data.

Next, in response to the switching from the offset adjustment mode to the normal operation mode, the changeover switch 13 has the terminal b.
Switched to the side. During this normal operation, the adder 11d
Supplies the tracking error signal supplied via the input terminal 17 to one end side, and the offset canceling output voltage for the tracking error signal is supplied. At this time, the lookup table 11a treats the output value from the position sensor 10 as address data and outputs offset data corresponding to this address. The lookup table 11a performs D / A conversion on the offset data, and supplies a voltage for offset cancellation to the adder 11d. The adder 11d outputs to the phase compensation circuit 14 a tracking error signal in which the offset included in the tracking error signal is canceled by this addition processing.

The phase compensation circuit 14 supplies the phase-compensated tracking error signal to the drive circuit 14 via the changeover switch 13. The drive circuit 14 drives the tracking actuator 16 to cancel the displacement of the objective lens.

Here, the offset zero detection circuit 11 is described.
e will be described with reference to the circuit diagram of one specific example shown in FIG. Here, the offset detection circuit 11c of FIG.
The same reference numerals are given to the parts in common with. The tracking error signal is supplied to the peak hold circuit 111 and the bottom hold circuit 112 via the input terminal 17.
The configurations of the peak hold circuit 111 and the bottom hold circuit 112 are the same as those of the peak hold circuit 111 and the bottom hold circuit 112, which are the main parts of the offset detection circuit shown in FIG. Omit it.

The final stage comparison amplifier 111b of the peak hold circuit 111 supplies the output signal to the inverting terminal via the resistor R5. Further, the comparison amplifier 112c at the final stage of the bottom hold circuit 112 supplies the output signal to the non-inverting terminal via the resistor R4. The comparison amplifier 113a feeds the output signal back to the inverting terminal of the comparison amplifier 113a via the feedback resistor R6, and supplies the output signal to the non-inverting terminals of the two comparison amplifiers 115a and 115b forming the window comparator 115, respectively. There is. The non-inverting terminals of these comparison amplifiers 115a and 115b have a voltage range of voltage + V and voltage −V and three resistors R.
The reference voltage divided by 8, R9, and R10 is supplied and compared with the voltage of the output signal from the comparison amplifier 113a.

In the offset adjustment mode, the comparison amplifiers 115a and 115b of the window comparator 11 are operated by the CPU 11 when the binary output combination to be output is "(1, 1)".
b is judged to be "+". Comparison amplifiers 115a and 115b
Is the CPU when the binary output combination is “(0,0)”
11b is judged as "-". Further, when the combination of binary outputs is “(0,1)”, the CPU 11b determines that the offset cancellation amount is appropriate as “0”, and stores this value in association with the output of the position sensor 10. . Offset zero detection circuit 11e even in the normal operation mode
May function to determine whether the offset is included in the tracking error signal.

With such a configuration, the offset adjustment mode is performed, for example, when the optical disc is replaced, or when the spindle motor reaches a certain number of revolutions during spin-up, and is supplied in the normal operation mode. The offset of the tracking error signal generated can be canceled.

Further, a third embodiment of the offset adjusting section 1 in the optical disk device will be described with reference to the block diagram shown in FIG. Here, common parts are given the same reference numerals, and description thereof is omitted. The offset adjustment unit 1 of FIG. 6 also has a CPU 11b, an offset detection circuit 11c, an adder 11d, an oscillator 12, and a changeover switch 13 as in the first embodiment.

Here, the offset adjusting unit 1 is shown in FIG.
A multiplying unit 11f is provided instead of the lookup table 11a shown in FIG. The multiplication unit 11f is provided with the offset detection circuit 1 for the displacement amount of the position sensor 10.
The inclination obtained from the offset of 1c is supplied as a multiplier, and the multiplier is provided to multiply the multiplier with the displacement amount and output the offset value. In addition, the CPU 11
Reference numeral b indicates the switching control of the changeover switch 13, and the offset detection circuit 11c for the displacement amount of the position sensor 10.
And calculates the multiplier from the offset of
It is used as a control means for controlling the supply to the. The multiplication unit 11f will be described in detail later with reference to the circuit diagram.

The operation of the offset adjusting section 1 shown in FIG. 7 will be described. The changeover switch 13 is switched to the terminal a side in the offset adjustment mode. In this offset adjustment mode, the oscillator 12 supplies the output to the drive circuit 15 via the changeover switch 13. In the oscillator 12, an objective lens (not shown) by a tracking actuator 16 according to the output of the oscillator 12 causes the radial direction of the optical disc to vibrate according to the oscillation amplitude. For the displacement of the objective lens by the tracking actuator 16, the position sensor 10 detects a value corresponding to the displacement amount. The position sensor 10 multiplies this value by the multiplication unit 1
It is supplied to 1f and CPU 11b. Also, the input terminal 17
The tracking error signal supplied via the offset detection circuit 11c detects the offset amount included in the tracking error signal, and outputs a value indicating the offset amount to the CPU 11b.

The CPU 11b takes in the value of the displacement amount and the value of the offset amount, respectively, and determines that the relationship between these two values is a first-order relationship. The calculation is controlled so as to obtain the slope of. The CPU 11b controls the supply of this inclination to the multiplication unit 11f. The multiplication unit 11f multiplies the output value of the position sensor 10 supplied to the multiplication unit 11f by the supplied inclination to calculate an absolute value equal to the value of the offset amount,
Since it is output for offset cancellation, the polarity is inverted and output as an offset cancellation value C
It is under the control of the PU 11b.

By performing the above-described operation, the offset cancel value of this optical disk device is output. Therefore, if only the value of the calculated reverse polarity of the inclination is held, it corresponds to the output value of the position sensor 10. It becomes possible to easily output the offset cancellation value.

Next, in response to the switching from the offset adjustment mode to the normal operation mode, the changeover switch 13 is operated by the terminal b.
Has been switched to the side. Input terminal 1 during normal operation
The multiplying unit 11 f that cancels the offset amount included in the tracking error signal supplied via 7 multiplies the value actually supplied from the position sensor 10 by the multiplying unit 11 f.
Through f, the magnification and polarity required for offset cancellation are changed and the result is supplied to the one end side of the adder 11d. The adder 11d supplies the tracking error signal including no offset to the phase compensation circuit 14. The phase compensation circuit 14 supplies the phase-compensated tracking error signal to the drive circuit 15 via the changeover switch 13. The drive circuit 15 drives the tracking actuator 16 to cancel the displacement of the objective lens.

Now, the multiplication section 11f will be described with reference to the circuit diagram of one specific example shown in FIG. The multiplication unit 11 f receives the position sensor 1 via the input terminal 18.
The information about the displacement of the objective lens, which is supplied from 0, is supplied to the multiplication IC 120, and the displacement information is converted into a digital value via the A / D converter 121, and the CPU 1
Output to 1b. The CPU 11b is the CPU 1
Since the offset is canceled assuming that the relationship between the offset amount supplied to 1b and the digital displacement information has a primary relationship, the slope of the reverse polarity is calculated and supplied to the D / A converter 122 shown in FIG. The D / A converter 122 converts the supplied inclination value into an analog signal and multiplies the IC 120.
Supply to one end side of. The multiplication IC 120 multiplies the voltage indicating the displacement information by the converted analog signal and outputs a voltage for offset cancellation to the adder 11d.

Since this circuit configuration requires a smaller circuit size than the first and second embodiments described above, the cost can be reduced most easily.

The look-up table 11a used in the first and second embodiments can be implemented by the block configuration shown in FIG. The displacement information from the position sensor 10 is supplied to the memory 130 that stores the data for offset cancellation, and is also supplied as address information to the CPU 11b via the address bus ADB. The memory 130 can be constituted by, for example, a RAM or an E ² PROM which is an electrically erasable ROM. In the memory 130, the data corresponding to the address information is transferred to the D / A converter 131 via the data bus DB.
Is output to the CPU 11b. D / A converter 131
Supplies an offset cancel output voltage to the adder 11d.

The position sensor 10 used in the above-described embodiment detects, for example, two-split light by reflecting the beam emitted from the light emitting diode 101 by the mirror 102 arranged on the side surface of the optical disc as shown in FIG. Irradiate the container 103. The two-divided photodetector 103 in the position sensor 10 sends detection signals from the respective detectors to the amplifiers 104 and 105. The amplifier 104 inputs to one end side of the adder 106 for addition, and the amplifier 105
The difference signal between these detection signals is input to the other end of the adder 106 as it is as an analog value and is also supplied to the A / D converter 107. The A / D converter 107 converts the supplied difference signal into a digital value and supplies it as displacement information to the look-up table 11a or the multiplication unit 11f and the CPU 11b described above.

By constructing the offset adjusting unit 1 in this way, it is not necessary to make the thread follow a high rotation speed, so that power consumption and heat generation can be reduced and the cost of the apparatus can be reduced. It is possible to greatly contribute to the improvement of productivity and reliability by using the optical pickup manufacturing technology at the present time.

Finally, the configuration and the operation of reading data from the optical disc will be described with reference to FIG. 10 for the optical disc device to which the offset adjusting section is applied. In this configuration, the laser light emitted from the laser diode 20 is applied to the disk 24 via the collimator lens 21, the beam splitter 22, and the objective lens 23. The return light reflected by the disk 24 is
The light is focused on a split photodetector 26 through an objective lens 23, a beam splitter 22, a multi-lens 25 including a cylindrical lens and a condenser lens. The divided photodetector 26 outputs each output photoelectrically converted from the divided photodetector 26 to the head amplifier 2
Output to 7. The head amplifier 27 amplifies each output and outputs it to the matrix amplifier 28.

The matrix amplifier 28 adds / subtracts the supplied outputs to output a focus error signal, a tracking error signal, and an RF signal, respectively. The focus error signal and the tracking error signal are supplied to the phase compensation circuit 29 and the offset adjustment unit 1, respectively. The drive circuit 30 based on the output signal from the phase compensation circuit 29 drives the focus actuator 31 based on the supplied focus error signal,
The objective lens 23 is moved.

The optical disk device is provided with a position sensor 10 and an offset adjusting section 1 for canceling the offset included in the tracking error signal.
The offset adjustment unit 1 includes an offset detection / correction circuit 11,
It is composed of an oscillator 12 and a changeover switch 13. The objective lens 23 is displaced by driving the tracking actuator 16. The displacement of the objective lens 23 supplies the detection signal from the position sensor 10 to the offset detection / correction circuit 11.

In the offset adjustment mode in which the offset amount for adjustment during normal operation is detected in advance, the changeover switch 13
Is switched to the terminal a side. By this switching, the oscillator 12 supplies the oscillating amplitude to the drive circuit 15. The drive circuit 15 supplies a drive signal to the tracking actuator 16 to drive it. The position sensor 10 detects the displacement of the objective lens 23 and supplies it to the offset detection / correction circuit 11. The offset detection / correction circuit 11 sets a value of the offset amount according to the supplied displacement amount for canceling the offset amount, or an inclination for offset cancellation.

In the offset adjusting section 1 of FIG. 10, the changeover switch 13 is set to the terminal b side, and shows the state in the normal operation. The offset detection / correction circuit 11 cancels the offset included in the tracking error signal output from the matrix amplifier 28 to cancel the offset.
Supply to 4. The phase compensation circuit 14 sends a tracking error signal that does not include an offset to the drive circuit 15 and the phase compensation circuit 40 via the changeover switch 13. The drive circuit 15 outputs a drive signal for the tracking actuator 16 to drive the tracking actuator 16. The tracking actuator 16 is driven in such a manner that the tracking error signal is corrected and no offset occurs.

Further, the phase compensating circuit 40 corresponding to the eccentricity of the disk phase-compensates the tracking error signal including no offset and outputs it to the drive circuit 41. The drive circuit 41 includes a sled actuator 42.
The optical pickup unit is moved to a desired track position according to a drive signal for driving the. At this time, since the tracking error signal that does not include the offset, that is, the corrected tracking error signal is used, the sled actuator 4
In No. 2, regardless of the number of rotations of the disk 24 by the spindle motor 50, sled servo can be applied to deal with eccentricity of the disk.

Generally, it is not possible to apply the thread servo to the eccentricity of the disk at the time of seek,
The fluctuation of the objective lens 23 causes an offset in the tracking error signal. However, by performing correction control so that the tracking error signal does not include an offset in accordance with the shake of the objective lens 23, the objective lens 23 can always be arranged at a predetermined position.

With this structure, the optical disk device does not need to be provided with a device capable of following a high rotation speed by applying the thread servo regardless of the rotation speed of the disk, and measures for power consumption and heat generation are eliminated. It can be avoided. Since the optical disk device does not need to use a component that can follow a high rotation speed, the cost of the device can be reduced more than the case where the above component is used.

Further, by suppressing the shaking of the objective lens even if the sled is moved during the seek operation, the settling time until the tracking servo is applied becomes unnecessary, so that the tracking servo can be applied quickly and the seek time can be increased. Can be shortened.

[0066]

According to the optical disk device of the present invention,
When the tracking control is performed so that the beam irradiated on the optical disc through the objective lens follows the recording track, the displacement amount detecting means detects the displacement amount of the objective lens, and the offset detection correcting means detects the displacement amount in advance during the offset adjustment. The offset value and the displacement amount of the objective lens are set to be associated and held, and the offset detection correction means corrects the offset amount of the tracking error signal in accordance with this setting during normal operation, and when the optical disk device is read. There is no need to provide a good tracking servo during writing and writing, and to provide a device that can follow a high rotation speed by applying a thread servo regardless of the disk rotation speed, thus avoiding measures for power consumption and heat generation. be able to. The cost of the device can be reduced as compared with the case where a component capable of following a high rotation speed is used.

Further, by suppressing the shake of the objective lens even if the sled is moved during the seek operation, the settling time until the tracking servo is applied is unnecessary, so that the tracking servo can be applied promptly and the seek time can be increased. Can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic block configuration of an offset detection / correction unit applied to an optical disk device according to the present invention.

FIG. 2 is a schematic block diagram of a first embodiment of the offset detection / correction unit shown in FIG.

3 is a circuit diagram showing an example of a more specific circuit of the offset detection circuit shown in FIG.

FIG. 4 is a schematic block diagram of a second embodiment of the offset detection / correction unit shown in FIG.

5 is a circuit diagram showing an example of a more specific circuit of the offset zero detection circuit shown in FIG.

FIG. 6 is a schematic block diagram of a third embodiment of the offset detection / correction unit shown in FIG.

FIG. 7 is a circuit diagram showing an example of a more specific circuit of the multiplication unit shown in FIG.

8 is a circuit diagram showing a specific configuration of the look-up table shown in FIGS. 2 and 4. FIG.

FIG. 9 is a block diagram showing a specific example of a position sensor to which the optical disk device according to the present invention is applied.

FIG. 10 is a block diagram showing a schematic configuration when an offset detection / correction unit is applied to the optical disc device according to the present invention.

FIG. 11 is a block diagram showing a schematic configuration of a conventional optical disc device.

[Explanation of symbols]

 1 --- Offset adjuster 10 --- Position sensor 11 --- Offset detection / correction circuit 11a --- Look-up table 11b --- ... CPU 11c ..... offset detection circuit 11d ..... adder 11e ..... offset zero detection circuit 11f ..... multiplication unit 12 ...・ ・ ・ Oscillator 13 ・ ・ ・ ・ ・ ・ Changeover switch 14 ・ ・ ・ ・ ・ Phase compensation circuit 15 ・ ・ ・ ・ ・ ・ Drive circuit 16 ・ ・ ・ ・ ・ ・ Tracking actuator 17 ・ ・ ・・ ・ ・ ・ ・ Input terminal ・ ・ ・ ・ ・ ・ ・ Output terminal

Claims (4)

[Claims] 1. A displacement amount detecting means for detecting a displacement amount of the objective lens in an optical disc device for performing tracking control in which a beam irradiated to an optical disc through an objective lens follows a recording track, and the displacement amount detecting means. Offset detection and correction means for detecting the offset included in the tracking error signal in accordance with the detection signal from, and holding the detected offset during offset adjustment to correct the offset amount of the tracking error signal obtained during normal operation. An optical disk device characterized by having. 2. The offset detection / correction means includes an offset detection means for detecting an offset included in an input tracking error signal, and an oscillation means for outputting an oscillation signal for vibrating the objective lens in the radial direction of the optical disc. A lookup table that outputs an offset cancel voltage according to the output of the displacement amount detection means; an addition means that adds an output signal from the lookup table and a tracking error signal that is input; The switching means for switching the oscillation signal and the output signal from the adding means, and the output from the offset detecting means corresponding to the switching control of the switching means and the output of the displacement amount detecting means are supplied to the look-up table. 2. A control means for performing data rewriting control according to claim 1, The optical disk device described. 3. The offset detecting / correcting means includes an oscillating means for outputting an oscillating signal for oscillating the objective lens in a radial direction of the optical disc, and an offset zero for detecting the presence / absence of an offset included in a supplied tracking error signal. Detecting means; a look-up table for outputting an offset cancel voltage according to the output of the displacement amount detecting means; an adding means for adding an output signal from the look-up table and an input tracking error signal; Switching means for switching between the oscillation signal from the means and the output signal from the adding means, the look-up table according to the switching control of the switching means, the output of the displacement amount detecting means, and the output result of the offset zero detecting means. Control means for controlling rewriting of the offset value output by the The optical disk device according to claim 1, wherein: 4. The offset detection / correction means includes an offset detection means for detecting an offset included in an input tracking error signal, and an oscillation means for outputting an oscillation signal for vibrating the objective lens in the radial direction of the optical disc. A multiplying means for supplying an inclination obtained from the offset of the offset detecting means to the displacement amount of the displacement amount detecting means as a multiplier, and multiplying the multiplier by the displacement amount to output an offset value; Means for adding the tracking error signal to the input and the switching signal for switching the oscillation signal from the oscillating means and the output signal from the adding means, the switching control of the switching means, and the displacement amount detection. The multiplier is calculated from the offset of the offset detecting means with respect to the displacement amount of the means, and the multiplier is calculated. 2. The optical disk device according to claim 1, further comprising a control unit that controls the supply of the optical disc.