JPH04245035A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To automatically correct the out-of-focus condition of the title device produced when the device is used for a long period. CONSTITUTION:An arithmetic section 72 finds the maximum and minimum amplitude values of a tracking error signal S34 at the time of seeking operations. Another arithmetic section 73 finds the optimum focus offset at which the amplitude of the signal S34 becomes the maximum and makes an offset setting section 74 to readjust the offset of focus servo.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to optical information recording and reproducing devices such as write-once type or read-only type optical disk devices, or erasable/rewritable magneto-optical disk devices, and in particular, to optical information recording and reproducing devices such as write-once type or read-only type optical disk devices, or erasable/rewritable magneto-optical disk devices. The present invention relates to an optical information recording/reproducing device having the following.

0002

[Prior Art] Conventionally, technologies in this field include:
Kazuo Terada, “Key Points of Optical Pickup System Design”, [
6] (1980-10-31) Japan Industrial Technology Center, P
．． There were those described in 151, 152, 161.

As described in this document, conventional optical information recording and reproducing devices, such as optical disk devices, emit a light beam onto an optical disk and detect focus errors and tracking errors from the reflected light. The optical pickup is equipped with an optical pickup that detects (a trace error with respect to a track of an optical disk) and outputs a detection signal for controlling focus servo and tracking servo. Further, a servo error signal generation means for outputting a focus error signal and a tracking error signal from the detection signal, a drive means for outputting a focus drive current and a tracking drive current based on the focus error signal and the tracking error signal, An actuator is provided that moves the optical pickup in the focusing direction and the tracking direction using a focusing drive current and a tracking drive current.

In this optical disk device, the optical disk is rotated by, for example, a spindle motor, and a focus error signal and a tracking error signal are output from a servo error signal generating means. Then, based on the focus error signal and the tracking error signal, feedback control (servo) is performed so that the drive means moves the optical pickup in the focus direction and the tracking direction via the actuator to eliminate the focus error and the tracking error, The information on the optical disc is read out.

[0005] In this type of optical information recording/reproducing device, the recording medium is an optical disk or a magneto-optical disk (
These are collectively referred to as "optical discs").
Since information is recorded and reproduced by optical means, it has the characteristics of large capacity and long life, and is used for various purposes such as document files.

[0006]

[Problems to be Solved by the Invention] However, the apparatus having the above structure has the following problems.

[0007] Since optical discs are characterized by long lifespan (for example, 10 years or more) and large capacity, it is desirable that the device also have a long lifespan. In addition, efforts are being made to increase the capacity of optical discs by increasing the bit density and track density, but the focus tracking error is ±1 μm.
A servo that follows with high precision, within 100 degrees, is required. Therefore, when the device is used for a long period of time, there is a high possibility that defocus will occur due to deflection of the device base on which the optical pickup is attached, deterioration of elements provided in the optical pickup, and the like. If the focus shifts, the light beam irradiated onto the optical disc will not be focused, and normal recording and reproduction performance will deteriorate or become impossible.

However, in conventional devices, for example, after the focus offset is adjusted by the manufacturer at the time of product shipment, the device base may flex due to long-term use by the user.
Alternatively, even if a focus shift occurs due to gradual deterioration of the element, it is difficult for the user to adjust the focus shift because there is no means for readjusting the focus offset. Therefore, due to focus shift due to long-term use, the S/N (signal/noise ratio) of the playback signal recorded on the optical disc decreases, resulting in a decrease in the reading rate or the track address or sector address pre-formed on the optical disc. etc. could not be read and recorded.

The present invention provides an optical information recording and reproducing apparatus that solves the problem of the prior art, which is the occurrence of defocusing due to long-term use.

0010

[Means for Solving the Problems] In order to solve the above problems, the present invention irradiates a light beam onto an optical disk and outputs a detection signal for controlling a focus servo and a tracking servo from the light from the optical disk. an optical pickup; a servo error signal generation means for outputting a servo error signal for the focus servo and the tracking servo based on the detection signal; and a drive means for outputting a drive current for focus and tracking based on the servo error signal; The optical information recording/reproducing apparatus includes an actuator for moving the optical pickup in a focusing direction and a tracking direction using the driving current, and a focus offset adjusting means is provided.

[0011] The focus offset adjustment means determines a focus offset at or near the maximum amplitude of the detection signal from the maximum amplitude value and minimum value of the detection signal during a seek operation for moving the optical pickup to a target track, and It has a function of readjusting the offset of the focus servo using focus offset.

0012

[Operation] According to the present invention, since the optical information recording/reproducing device is configured as described above, for example, after power is turned on or after disc loading (installation), the optical pickup moves along the radial direction of the optical disc to the home position. The optical disc rotates and starts focus servo. Furthermore, after track servo is started and recording/reproducing operation becomes possible, a seek operation is performed to move the optical pickup to the target track.

In this seek operation, the focus offset adjustment means detects the amplitude of the detection signal for focus servo or tracking servo control, finds the focus offset where the amplitude is at or near the maximum, and adjusts the focus offset to the found focus offset. Based on this, the focus servo offset is readjusted.

[0014] As a result, the offset of the focus servo is automatically adjusted to correct the focus shift, and normal recording and reproducing operations can be performed even after long-term use. Therefore, the above problem can be solved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, and is a block diagram of a magneto-optical disk device which is one of optical information recording and reproducing devices.

In this magneto-optical disk device, an optical pickup 10 is provided near an optical disk 1 that is rotated by, for example, a spindle motor.

The optical pickup 10 irradiates a light beam onto the optical disc 1 and outputs a detection signal FE for focus servo control and a detection signal TE for tracking servo control from the reflected light, and also records information on the optical disc 1. It has a function of outputting reproduction detection signals PD1 and PD2.

This optical pickup 10 includes a semiconductor laser 11, beam splitters 12 and 14, an objective lens 13,
It has a quarter wavelength plate 15, a polarizing beam splitter 16, a photodetector 17 for outputting a reproduction detection signal PD1, and a photodetector 18 for outputting a reproduction detection signal PD2. Furthermore, a laser mirror 19, a two-part photodetector 20 for outputting a detection signal TE for tracking servo control, a cylindrical lens (plano-convex lens) 21, and a detection signal F for focus servo control.
For example, a two-part photodetector 2 for outputting E.
2 is provided.

A servo error signal generating means 30 is connected to the output sides of the photodetectors 20 and 22. The servo error signal generation means 30 generates detection signals FE and TE.
is input, and the servo error signal for the focus servo and tracking servo, that is, the focus error signal S3
1, S33 and tracking error signals S32, S34
This is a circuit that generates and amplifies it.

The servo error signal generation means 30 includes a differential amplifier 31 that generates a focus error signal S31 from the detection signal FE, a differential amplifier 32 that generates a tracking error signal S32 from the detection signal TE, and a focus error signal S31. and an amplifier 34 that amplifies the tracking error signal S32 and outputs the amplified tracking error signal S34.

A driving means 50 is connected to the output side of the amplifier 33 via a phase compensation circuit 40 for compensating for phase delay and lead, and a notch filter (narrow band filter) 42 for preventing focus high-order resonance. has been done. On the other hand, a driving means 50 is connected to the output side of the amplifier 34 via a phase compensation circuit 41.

The driving means 50 performs voltage/current conversion of the output of the notch filter 42 to obtain a focusing driving current If.
a focus side drive unit 51 that outputs
1 and a tracking side drive section 52 that performs voltage/current conversion of one output and outputs a tracking drive current It. An actuator 60 equipped with an optical pickup 10 is connected to the output side of the drive means 50.

The actuator 60 moves the objective lens 13 in the focus direction by means of an objective lens vertical drive coil operated by a focus drive current If, and also moves the optical pickup 10 in the radial direction of the optical disk 1 by a tracking drive current It. It is something.

Further, a focus offset control means 70, which is a feature of this embodiment, is connected between the output side of the amplifier 34 and the input side of the amplifier 33. The focus offset adjustment means 70 has a function of automatically adjusting the focus servo offset (focusing offset) so that the amplitude of the tracking error signal S34 obtained during the seek operation to move the optical pickup 10 to the target track is at or near the maximum amplitude. have.

The focus offset adjustment means 70 includes, for example, an analog/digital converter (hereinafter referred to as A/D converter) 71 that converts an analog tracking error signal S34 into a digital signal, and a maximum value register and a minimum value register. and a maximum/minimum value calculation unit 72 for calculating the maximum and minimum values of the digital tracking error signal S71 output from the A/D conversion unit 71. Furthermore, an optimum offset calculation section 73 which calculates the optimum focus servo offset based on the output of the maximum/minimum value calculation section 72 and a digital/analog converter (hereinafter referred to as a D/A converter) is provided. An offset setting section 74 is provided which supplies an output signal S74 for setting a focus servo offset based on the calculation result of step 73 to the input side of the amplifier 33.

The maximum/minimum value calculating section 72 and the optimum offset calculating section 73 may be constructed of individual circuits such as arithmetic circuits, or may be executed under program control of a central processing unit (hereinafter referred to as CPU). There is.

FIG. 2 is a circuit diagram showing an example of the configuration of the amplifier 33 on the focus servo side in FIG.

The amplifier 33 is an inverting amplifier circuit consisting of an operational amplifier circuit A0, an input resistor Ri1 to which the focus error signal S31 is input, an input resistor Ri2 to which the output signal S74 of the offset setting section 74 is input, and a feedback resistor Rf. It consists of In addition, (+) of the operational amplifier circuit A0
The side input terminal has a reference voltage (e.g. ground potential)
V0 is applied.

In this amplifier 33, the offset setting section 7
By inputting the output signal S74 of No. 4 to the input resistor Ri2, the offset changes.

The (1) servo operation, (2) automatic focus shift correction method, and (3) focus shift correction method of the magneto-optical disk device configured as described above will be explained.

(1) Servo operation A light beam emitted from the semiconductor laser 11 in the optical pickup 10 passes through the beam splitter 12 and is focused onto the optical disk 1 by the objective lens 13 . The reflected light from the optical disk 1 passes through an objective lens 13 and a beam splitter 12, and is further split into beams for servo control and signal detection by a beam splitter 14. The separated beam for signal detection passes through a quarter-wave plate 15, is separated by a polarizing beam splitter 16, and is received by photodetectors 17 and 18.

Adding the reproduction detection signals PD1 and PD2 output from the photodetectors 17 and 18, respectively (=P
D1+PD2), the preformat signal is reproduced. Further, by taking the differential (=PD1-PD2) of the reproduction detection signals PD1 and PD2, the magneto-optical signal is reproduced.

On the other hand, the servo signal beam split by the beam splitter 14 in the optical pickup 10 is split by a laser mirror 19 into two parts, one for tracking and the other for focusing. The light is received by the two-segment photodetector 20. The focusing beam passes through a cylindrical lens 21 and is received by a two-part photodetector 22 . One photodetector 20 outputs a detection signal TE for tracking servo control, and the other photodetector 22 outputs a detection signal FE for focus servo control.
1 respectively.

The differential amplifier 31 receives the detection signal FE and outputs a focus error signal S31. The differential amplifier 32 receives the detection signal TE and outputs the tracking error signal S32. The focus error signal S31 is
The amplified focus error signal S33 is amplified by the amplifier 33, and the focus error signal S33 is subjected to phase lag and lead phase compensation in the phase compensation circuit 40, and is then provided to the drive unit 51 via the notch filter 42. .

The output of the notch filter 42 is transmitted to the drive section 51.
As a result, voltage/current conversion is performed, and the focus drive current If is output from the drive unit 51 and supplied to the actuator 60. The actuator 60 moves the objective lens 1 by means of an objective lens vertical drive coil provided inside.
Focusing control is performed by moving 3 up and down.

Further, the tracking error signal S32 outputted from the amplifier 32 is amplified by the amplifier 34, the amplified tracking error signal S34 is phase compensated by the phase compensation circuit, and voltage/current converted by the drive section 52. The tracking drive current I from the drive unit 52
t is output. The actuator 60 is driven by this tracking drive current It, and tracking control is performed.

As described above, the rotating optical disk 1
The objective lens 13 is driven so as to irradiate a precisely focused light beam onto the optical disc 1 in response to the surface wobbling,
A focusing operation is performed. Furthermore, optical disc 1
A tracking operation is performed along a track pre-stamped (formed) on the top, and a focus error signal S3 is generated.
Servo is performed so that the tracking error signal S32 becomes 1 and the tracking error signal S32 becomes 0, and data recording/reproducing operations are performed.

(2) Method for automatically correcting focus deviation A method for automatically correcting focus deviation during long-term use will be explained with reference to FIGS. 3 to 5.

Note that FIG. 3 is a waveform diagram showing the tracking error signal S34 etc. during a seek operation to move the optical pickup to the target track, and FIG. 4 is a waveform diagram showing the focus error signal S34.
33 and the distance from the optical disc 1, and FIG. 5 shows the focus offset and tracking error signal S.
34 is a diagram showing the relationship with the amplitude of .34.

First, power is turned on or disk loading is performed, and the optical pickup 10 is moved to the actuator 6.
0 to move to the home position and optical disc 1
rotates. Then, a focus search operation is started by a control signal from a control circuit (not shown) including a CPU or the like, and a focus servo is operated. Further, after the track servo is activated and recording/reproducing operation is enabled, a seek operation is generally performed to move the optical pickup 10 to a target track.

In the seek operation, the track servo is turned off and the optical pickup 10 is moved. At this time, the tracking error signal S34 output from the amplifier 34
traverses a plurality of tracks as the optical pickup 10 moves, so it has a waveform as shown in FIG.

[0042] S35 in FIG. 3 is a seek operation section, and S36
is the seek start section, S37 is the section immediately before the end of the seek, S
38 indicates the operating speed profile of the optical pickup 10, respectively.

The depression at the center of the tracking error signal S34 in FIG. 3 becomes a high-frequency signal during high-speed movement, and the amplitude decreases due to the frequency characteristics of the detection section. Therefore, an accurate tracking error signal S34 is detected only in the seek start section S36 or the section S37 immediately before the end of the seek. Therefore, in the section S36 or S37 of FIG. 3, the accurate maximum amplitude TEmax and minimum amplitude TE
A tracking error signal S34 that oscillates between min is obtained.

On the other hand, during focus search, as shown in FIG. 4, when the objective lens 13 is moved up and down with the focus position 0 as the center, the focus error signal S33 has a curved waveform that changes up and down with the focus position 0 as the center. Become. Here, if a focus shift occurs, a focus error signal S3
3 is a curve like a broken line, and the focus position 0 is shifted.

As described above, when a focus shift occurs, the amplitude of the tracking error signal S34 obtained when only the focus servo is operated decreases from the amplitude peak point P at the focus position 0, as shown in FIG. In other words, even if a focus shift occurs, the focus shift can be corrected by adding a focus servo offset (focusing offset) so that the amplitude of the tracking error signal S34 reaches its peak.

(3) Focus shift correction method The focus shift correction method will be explained in detail with reference to FIGS. 6 and 7.

Note that FIG. 6 is a flowchart of maximum and minimum value calculations in the focus offset adjustment means 70 in FIG. 1, and FIGS. 7 and 8 are flowcharts of focus offset setting.

(3) (A) Flowchart of FIG. 6 In the focus offset adjustment means 70 of FIG. 1, the tracking error signal S34 is converted into a digital signal by the A/D converter 71. The tracking error signal S71 converted into a digital signal is converted into the maximum value of the digital tracking error signal S71 (T in FIG.
Emax) and the minimum value (TEmin in FIG. 4) are calculated.

That is, in the flowchart of FIG. 6, when maximum and minimum value calculations are started, in step 100,
The minimum value register Rmin in the maximum/minimum value calculation unit 72 has an initial value of, for example, 10000, and the maximum value register Rmax.
For example, 0 is set as an initial value. Step 101
Then, it is determined whether the value of the tracking error signal S71 is smaller than the content of the minimum value register Rmin. If it is smaller, the content of the minimum value register Rmin is replaced with the value of the tracking error signal S71 in step 102. In step 101, when the value of the tracking error signal S71 is larger than the content of the minimum value register Rmin,
The contents of the minimum value register Rmin remain unchanged.

Next, in step 103, it is determined whether the value of the tracking error signal S71 is greater than the content of the maximum value register Rmax. When the value is larger than the value of the maximum value register Rmax, the contents of the maximum value register Rmax are replaced with the value of the tracking error signal S71 in step 104, and when the value of the tracking error signal S71 is smaller than the contents of the maximum value register Rmax, the contents of the maximum value register Rmax are left unchanged. shall be.

The above calculation process is repeated for, for example, 2 ms via step 105 to find the maximum and minimum values.

When the maximum and minimum value calculation processing is completed, focus offset setting processing is performed by the optimum offset calculation section 73 according to the flowcharts of FIGS. 7 and 8.

(3) (B) Flowcharts of FIGS. 7 and 8 In the focus offset setting process, as shown in FIG. 7, when the optimum offset calculation process is started, the optimum offset calculation unit 73 performs the following steps in step 200 The D/A converter constituting the offset setting section 74 is set to a value Vα that gives an offset of approximately 0, and is initialized. Then,
The output signal S74 of the offset setting section 74 is input to the input resistor Ri2 in the amplifier 33 shown in FIG. As a result, the amplification degree of the amplifier 33 changes, and the focusing offset of the focus servo system is set to approximately zero.

Next, in step 201, after the maximum and minimum value calculating section 72 calculates the maximum and minimum values of the tracking error signal S71 at the set offset,
In step 202, the optimum offset calculation unit 73 sets the current amplitude value Ai-1 to TEmax-TEmin. Further, in step 202, the offset application direction is set to offset + and Si-1 = 1, and step 203
Then, the D/A converter set value in the offset setting section 74 is set to Vα+ΔVα, and the focusing offset is set. Note that the + sign in step 203 may be either + or - as an initial value. ΔVα is a minute value, which is several tens of millivolts in terms of focusing offset.

After the initial settings in steps 200 to 203 are completed, in step 204, the offset Vα
Maximum value T of tracking error signal S71 at +ΔVα
Emax and minimum value TEmin are calculated by maximum and minimum value calculation unit 72.
Calculate with. Next, in step 205, the optimum offset calculation unit 73 calculates the new amplitude value Ai as Ai=TEm
Calculate from ax-TEmin.

Thereafter, the process proceeds to the flowchart of FIG. 8 via the symbol ■, and steps 206 to 210-1, 210-2
, and 211-1a, 211-1b, 211-2a, 2
11-2b, the old amplitude value Ai-1 and the new amplitude value Ai
and when the section S36/S37 has not ended (
In step 207), via step 208a, it is determined in step 209 whether the added offset ΔVα has increased or decreased the amplitude. As a result of the determination, when the amplitude is large, the process moves to step 210-1, and when the amplitude is small, the process moves to step 210-2, where it is determined whether to add or subtract the next offset.

For example, in step 211-1b, Vα=
Set Vα+ΔVα, Si−1 = 1, and set the new amplitude value Ai
If the difference a between and the old amplitude value Ai-1 becomes positive (step 209), it is determined that the offset has been increased by ΔVα and the amplitude has become large. Furthermore, in step 211-1b, similar processing is performed for points below with Vα+ΔVα, Si-1 =1.

Further, in step 211-1b, Vα=V
α+ΔVα, Si−1 = 1 is set, and if the difference a becomes negative, it is determined that the offset is increased by ΔVα and the amplitude has become small (step 209), and step 211-2b
Then, with Vα-2·ΔVα, Si-1 = 0, the process from step 204 onward in FIG. 7 is performed via the symbol ■. −2Δ
The reason why it is set as Vα is that at -ΔVα, the offset is the same as the previous calculation, resulting in wasted calculations.

The above operation is performed in section S36 or S37, or both sections S36 and S37 (step 20
7) Finely adjust the focus offset. Therefore, even if a magneto-optical disk device is used for a long period of time and a focus shift gradually occurs due to deflection of the device base or deterioration of an element, the focus shift can be automatically corrected.

Note that the present invention is not limited to the illustrated embodiment, and various modifications are possible. Examples of such modifications include the following.

(i) The focus offset adjusting means 70 in FIG. 1 adjusts the focus offset through arithmetic processing using digital signals, but it is also possible to configure this with other circuits. be. For example, based on the tracking error signal S34 output from the amplifier 34, the maximum amplitude value and the minimum amplitude value are determined using a time constant circuit consisting of a capacitor and a resistor, and the offset amount is determined from both values using an operational amplifier or the like. Even if the circuit configuration is such that the offset value is fed back to the input side of the amplifier 33, substantially the same advantages as in the above embodiment can be obtained.

(ii) In the above embodiment, a configuration was described in which the focus offset adjusting means 70 corrects the focus shift based on the amplitude of the tracking error signal S34, but it is also possible to correct the focus shift based on other signals. It is. For example, the focus offset adjustment means 70 uses the amplitude of the track cross signal, which is the sum signal of the two-segment photodetector 20 for tracking error detection, to correct the focus shift.
It is also possible to configure

(iii) Optical pickup 10 in FIG. 1
Also, the servo error signal generation means 30, etc. can be modified to have a circuit configuration other than that shown in the drawings.

(iv) Although the above embodiment has been explained using a magneto-optical disk as an example, the present invention can also be applied to a write-once type or read-only type optical disk device.

[0065]

As described in detail above, according to the present invention, since the focus offset adjustment means is provided, the detection signal for focus servo control or the tracking servo control is Based on the control detection signal, the amplitude of the signal is detected, and the focus offset is automatically adjusted to maximize the amplitude, thereby accurately correcting the focus shift.

Therefore, even if the device is used for a long period of time and there is a gradual focus shift due to deflection of the device base or deterioration of the device, the focus shift can be accurately corrected and accurate recording can be achieved. Regeneration operation can be expected for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a configuration of a magneto-optical disk device showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of the amplifier in FIG. 1;

FIG. 3 is a waveform diagram during a seek operation.

FIG. 4 is a diagram showing the relationship between focus error and distance from an optical disc.

FIG. 5 is a diagram showing the relationship between focus offset and tracking error signal amplitude.

FIG. 6 is a flowchart of maximum and minimum value calculations.

FIG. 7 is a flowchart of focus offset setting.

FIG. 8 is a flowchart of focus offset setting.

[Explanation of symbols]

1 Optical disc 10 Optical pickup 30 Servo error signal generation means 50 Driving means 60 Actuator

Claims (1)

[Claims] 1. An optical pickup that irradiates a light beam onto an optical disk and outputs a detection signal for controlling a focus servo and a tracking servo from the light from the optical disk, and an optical pickup for controlling a focus servo and a tracking servo based on the detection signal. a servo error signal generating means for outputting a servo error signal for use in the servo error signal; a driving means for outputting a driving current for focusing and tracking based on the servo error signal; and a driving current for moving the optical pickup in the focusing direction and the tracking direction using the driving current. In an optical information recording/reproducing apparatus, the amplitude of the detection signal is determined to be at or near the maximum amplitude from the maximum amplitude value and minimum amplitude value of the detection signal during a seek operation for moving the optical pickup to a target track. 1. An optical information recording/reproducing apparatus comprising: a focus offset adjusting means for determining a focus offset and readjusting the offset of the focus servo based on the focus offset.