KR20040062258A - A focus error control method, a speed control method thereof, and apparatuses therefor - Google Patents

Abstract

PURPOSE: A method for controlling a focus error is provided to detect size of surface vibration of a disk by using size of a DC offset of a focus error signal, and to change a gain of a focus servo in order to suppress an influence by the surface vibration, thereby stably performing a recording/reproducing operation. CONSTITUTION: A device detects size of a DC offset of a focus error signal in a current reproduction position(S602). The device compares the detected DC offset of the focus error signal with a predetermined reference voltage(S604). If the detected DC offset of the focus error signal is bigger than the predetermined reference voltage, the device increases a gain of a focus servo up to a disk circumference range from the current reproduction position(S606). The device obtains a focus servo driving signal by the set gain of the focus servo, and drives a focus actuator(S608).

Description

A focus error control method, a double speed control method using the same, and apparatuses suitable for the same {A focus error control method, a speed control method, etc. and apparatuses therefor}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive, and more particularly, to a focus error control method for controlling a magnitude of a focus error signal for a disk on which surface vibration occurs, a double speed control method using the same, and apparatuses suitable for the method.

Discs, which are optical record storage media, are ideal for flat disks without tilting. However, discs may be bent or twisted due to factors such as errors and deviations in the manufacturing process and carelessness of the user.

When recording or playing back data on the disc, surface vibration may occur due to the disc bending or other causes. If this surface vibration component exceeds the allowable range, normal data recording / reading is impossible. Therefore, there is a problem that data should be recorded / read out by lowering the speed of the disc.

The present invention has been devised to solve the above problems, and an object thereof is to provide a focus error control method for suppressing the influence of surface vibration of an optical disc.

Another object of the present invention is to provide a double speed control method to which the above-described focus error control method is applied.

Another object of the present invention is to provide devices suitable for the above methods.

1 is a diagram illustrating an example of a disc that is curved in the radial direction.

2 is a waveform diagram showing the influence of surface vibration on the focus error signal.

3 is a waveform diagram showing the effect of surface vibration on the RF signal.

4 is a waveform diagram showing a change in offset of a focus servo error signal in a tilted disc.

5 is a waveform diagram for schematically showing a focus error control method according to the present invention.

6 is a flowchart illustrating a focus servo control method according to the present invention.

7 is a graph showing a change in the dc offset of the focus error signal according to the disk double speed.

8 is a flow chart showing a preferred embodiment of a double speed control method according to the present invention.

9 is a block diagram showing a configuration of a disk drive according to the present invention.

Focus error control method according to the present invention for achieving the above object

In the focus servo control method of an optical disc recording and reproducing apparatus,

Detecting a dc offset of the focus error signal at the current position of the pickup; And

And changing the gain of the focus servo if the dc offset of the detected focus error signal is greater than a predetermined reference value Vref.

Here, it is preferable to compare the difference between the dc offset of the focus error signal measured at the inner circumference of the disk and the dc offset of the focus error signal at the current position with a predetermined reference value Vref.

In adjusting the gain of the focus servo, it is more preferable to adjust the gain of the frequency band corresponding to the surface vibration component.

Disc speed control method for achieving the above another object

In the focus servo control method of an optical disc recording and reproducing apparatus,

Rotating the optical disk at a predetermined speed;

Detecting a dc offset of the focus error signal at the current position of the pickup;

Rotating the disc at a set double speed if the dc offset of the detected focus error signal is less than a predetermined reference value Vref; And

And if the dc offset of the detected focus error signal is greater than the predetermined reference value Vref, changing the gain of the focus servo and rotating the disk at the set double speed.

An optical disc recording / reproducing apparatus according to the present invention for achieving the above another object is

A pickup unit irradiating a laser beam to the disk, receiving a laser beam reflected from the disk, and outputting an RF signal in an analog form corresponding to the amount of light of the received laser beam;

An RF amplifying unit amplifying and outputting an RF signal provided by the pickup unit with a predetermined amplification, and generating a focus error signal necessary for servo control from the RF signal;

A servo controller which controls the focus servo of the pickup unit in response to a focus error signal provided by the RF amplifier unit; And

It includes a control unit for controlling the above components,

Here, the control unit detects a dc offset of the focus error signal at the current position of the pickup unit, and controls the gain of the servo control unit if the dc offset of the detected focus error signal is greater than a predetermined reference value Vref. do.

An optical disc recording / reproducing apparatus according to the present invention for achieving the above another object is

A pickup unit irradiating a laser beam to the disk, receiving a laser beam reflected from the disk, and outputting an RF signal in an analog form corresponding to the amount of light of the received laser beam;

An RF amplifying unit amplifying and outputting an RF signal provided by the pickup unit with a predetermined amplification, and generating a focus error signal necessary for servo control from the RF signal;

A servo controller which controls the focus servo and the spindle servo of the pickup unit in response to a focus error signal provided by the RF amplifier; And

It includes a control unit for controlling the above components,

Here, the control unit controls the servo control unit to rotate the disk according to the set double speed, detect the dc offset of the focus error signal at the current position of the pickup unit, the dc offset of the detected focus error signal is a predetermined reference value Vref If smaller, the disk is rotated at the set speed, and if the dc offset of the detected focus error signal is greater than the predetermined reference value Vref, the gain of the focus servo is changed, and the disk is rotated at the set speed.

Hereinafter, the configuration and operation of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an example of a disc that is curved in the radial direction. A disk whose disk surface rises upward with respect to the flat reference plane is called a positive tilt disk, and a disk whose disk surface descends downward with respect to the reference plane is called a negative tilt disk. The positive tilt disc and the negative tilt disc are collectively called radial tilt discs.

2 is a waveform diagram showing the influence of surface vibration on the focus error signal. As shown in FIG. 2, it can be seen that a ripple component is generated every one rotation of the disc. This ripple component is caused by surface vibration, the magnitude of which is proportional to the deflection of the disk, i.e. the size of the tilt. In addition, the frequency of this ripple component is 2-3Khz. This ripple component is similarly generated in the tracking error signal, but the influence on the focus error is greater than the tracking error due to the characteristics of the surface vibration.

3 is a waveform diagram showing the effect of surface vibration on the RF signal. As shown in FIG. 3, it can be seen that the magnitude of the envelope of the RF signal is reduced where the ripple component occurs. The greater the surface vibration, the smaller the envelope size of the RF signal, and thus the lower the disc's playback performance. This can also be understood from the structural aspect of the pickup which generates the focus signal and the RF signal. That is, the focus error signal is defined as the diagonal difference signal of the received signals generated by the quadrature photodetector, and the RF signal is defined as the sum signal, so that the variation in the focus error signal is directly related to the variation in the RF signal. Can be understood intuitively.

4 is a waveform diagram showing a change in offset of a focus servo error signal in a tilted disc. As shown in FIG. 4, the magnitude of the offset of the focus servo error signal is proportional to the magnitude of the tilt and increases toward the outer circumference of the disk. The larger the offset, the greater the negative effect on the RF signal.

Therefore, it can be seen that it is necessary to suppress the influence of surface vibration in recording / reproducing data on the disc. In addition, the larger the tilt, the greater the surface vibration, the larger the magnitude of the ripple component and the offset in the focus signal, and the greater the negative effect on the RF signal. As a result, the envelope of the RF signal does not decrease according to the magnitude of the surface vibration. It can be seen that there is a need to avoid this.

The present invention proposes a method of determining the degree of surface vibration generated in the disk and adjusting the response characteristic of the focus error accordingly.

In the related art, there is a method of determining the degree of tilt and controlling the tilt of the disk accordingly. For example, there is a method of reading the signal recorded on the disc to determine the amount of jitter due to crosstalk, and adjusting the tilt adjusting means in accordance with the amount of jitter.

The magnitude of the crosstalk is proportional to the amount of tilt, and as the crosstalk increases, the amount of jitter also increases, so that the amount of tilt can be determined by the amount of jitter. Therefore, the disk is inclined in the opposite direction according to the determined jitter amount to compensate for the influence due to the tilt.

Meanwhile, a method of compensating the tilt of a disc by determining the tilt of the disc by the DC offset of the focus error signal is disclosed. Patent Publication No. 2002-67198 (published on Aug. 22, 2002) compares a dc offset of a focus drive signal set in an inner circumference with a dc offset of a focus drive signal at a reproducing position, and detects a degree of tilt. A method of compensating for tilt of a disc by controlling a tilt drive motor is disclosed.

However, even if the disc tilt is corrected according to the tilt amount detected by the dc offset of the focus error drive signal, as in Patent Publication No. 2002-67198, it is possible to prevent the negative influence of the RF signal due to the surface vibration component of the disc. none.

On the other hand, a method of limiting the maximum reproduction speed has also been proposed by determining whether the tilt according to the size of the focus error signal. For example, according to patent application 2002-60817 (filed Oct. 05, 2002) filed by the present applicant, the dc offset of the focus error signal is detected at n positions on the radius of the disk, and the detected focus error signals Disclosed are a method and apparatus for determining whether the disc is tilted and for limiting the maximum playback speed when the disc is tilted as a result of the determination.

However, in the case of the patent application 2002-60817, it can be seen that it is more effective to be able to reproduce at a higher double speed by suppressing an error due to the surface vibration of the disc rather than simply lowering the double speed.

5 is a waveform diagram for schematically showing a focus error control method according to the present invention. In FIG. 5, a solid line indicates a change in the dc offset of the focus error signal according to the first servo gain gain1, and a dotted line indicates the focus according to the second servo gains gain2 and gain2> gain1. This graph shows the change in the dc offset of the error signal.

The dc offset, i.e., the residual error ε, of the focus error signal according to the first servo gain gain1 increases toward the outer circumference along the radial direction of the disk. In other words, the influence of the surface vibration increases as the disk is moved toward the outer circumference in the radial direction.

In the present invention, if the dc offset of the focus error signal is greater than the predetermined reference voltage Vref, the gain of the focus servo is increased from the first servo gain gain1 to the second servo gain gain2.

If the servo gain is G, the magnitude Fe of the focus error driving signal is determined as in Equation 1 below.

Fe = ε / G

According to Equation 1, as the servo gain G increases, the size Fe of the focus error driving signal decreases, thereby slowing the servo response. In other words, when the surface vibration increases, the surface vibration component can be compensated by slowing down the servo response characteristic. Here, the overall gain of the focus servo may be adjusted, but only the gain in the frequency band corresponding to the surface vibration, that is, the band of 2-3Khz, may be adjusted.

6 is a flowchart illustrating a focus servo control method according to the present invention.

First, the magnitude of the dc offset of the focus error signal is detected at the current reproduction position (s602).

The dc offset of the detected focus error signal is compared with a predetermined reference voltage Vref. (S604) In practice, the difference between the dc offset of the focus error signal measured at the inner circumference of the disk in the initial operation of the disk, that is, the lead-in operation. Determines whether is greater than the predetermined reference voltage Vref.

If the dc offset of the detected focus error signal is greater than the predetermined reference voltage Vref, the gain of the focus servo is increased in the range from the current playback position to the outer periphery of the disk (s606).

The focus servo drive signal is obtained by the set focus servo gain to drive the focus actuator (s608).

In the method shown in Fig. 6, the reference voltage Vref is set to a value at which the reproduction signal is not affected by the surface vibration component.

7 is a graph showing a change in the dc offset of the focus error signal according to the disk double speed.

As shown in FIG. 7, the dc offset of the focus error signal changes according to the double speed. In general, as the double speed increases, the dc offset of the focus error signal increases, but decreases above a certain double speed. The reason for the decrease above any speed is that the factor that affects the surface vibration is dependent on the speed.

In the double speed control method according to the present invention, if the dc offset of the focus error signal is measured and the dc offset of the focus error signal is greater than the predetermined reference voltage Vref, the gain of the focus servo is increased to increase the gain of the focus servo without reducing the normal speed. It is characterized by enabling recording / playback.

8 is a flow chart showing a preferred embodiment of a double speed control method according to the present invention.

First, the dc offset and peak-peak value PEAK_l of the focus error signal are measured while rotating the disk at a predetermined double speed in the read-in operation of the disc. (S802) The double speed in the read-in operation differs for each type of disc. The speed is set to the normal speed, that is, the optimal speed for the disc.

The disk is rotated at a faster speed than the speed of lead-in operation (s804).

The dc offset and peak-peak value PEAK_c of the focus error signal at the reproduction position are measured (s806).

The peak-peak value PEAK_c measured at the playback position is compared with the peak-peak value PEAK_l set in the read-in operation. (S808) If the peak-peak value PEAK_c measured at the playback position is read-in, If it is greater than the set peak-peak value PEAK_l, the process proceeds to step s810 and rotates at a lower speed than the set speed.

If the peak-peak value PEAK_c measured at the playback position is not greater than the peak-peak value PEAK_l set in the read-in operation in step s808, the dc offset and lead-in of the focus error signal measured at the playback position measured at the playback position Compare the dc offset of the focus error signal set in the operation (s812).

If the dc offset of the focus error signal measured at the playback position measured at the playback position is not greater than the dc offset of the focus error signal set at the read-in operation, the process proceeds to step s814 to rotate the disk at the predetermined speed.

If the dc offset of the focus error signal measured at the playback position measured at the playback position in step S812 is greater than the dc offset of the focus error signal set in the lead-in operation, increase the gain of the focus servo and proceed to step s814 to set the disk (S816) Here, the overall gain of the focus servo may be adjusted, but only the gain in the frequency band corresponding to the surface vibration, that is, the band of 2-3Khz, may be adjusted.

According to the double speed control method shown in FIG. 8, when the disc is rotated at a high double speed, the magnitude of the dc offset of the focus error signal is detected, and if the magnitude of the dc offset of the detected focus error signal is larger than the predetermined reference voltage Vref, the focus is determined. By changing the gain of the servo, it is possible to stably record / play back without lowering the speed.

9 is a block diagram showing a configuration of a disk drive according to the present invention. The optical disc drive shown in FIG. 9 includes a disc 902, a pickup unit 904, an RF amplifier 906, a digital signal processor 908 (Digital Signal Processor, hereinafter referred to as a DSP), an interface unit 910, and a controller ( 912, a servo controller 914, and a driver 916.

The disc 902 may be a CD, CD-ROM, DVD, or the like as an optical recording / playback medium.

In the reading operation, the pickup unit 904 irradiates the laser light to the rotating disk 902, receives the laser light reflected from the disk 902, and receives an RF signal of an analog form corresponding to the light amount of the received laser light. Output On the other hand, in the recording operation, the pickup section 904 is configured to generate the laser light corresponding to the recording pulse provided from the recording modulation section 918 and to irradiate the disk 902.

The RF amplifier 906 amplifies and outputs an RF signal provided from the pickup unit 904 with a predetermined amplification degree. The RF signal amplified by the RF amplifier 906 is provided to the DSP 908. On the other hand, the RF amplifier 906 generates a focus servo error signal and tracking servo error signals necessary for servo control from the RF signal to provide to the servo controller 914.

In the reproducing operation, the DSP 908 demodulates and outputs the digital signal from the RF signal. In the recording operation, the DSP 908 modulates the data provided from the interface unit 910 and provides the modulated data to the recording modulator 918. The write modulator 918 generates a write pulse corresponding to the modulated data provided by the DSP 908 and provides it to the pickup unit 904.

The interface unit 910 interfaces with the host to allow data transmission and reception between the controller 912 and the DSP 908. An example of such an interface unit 910 is an IDE controller.

The controller 912 is responsible for controlling the components shown in FIG. 5, and particularly, performs the focus control operation and the double speed control operation according to the present invention. The controller 912 is implemented as a microprocessor and performs a control operation by a software routine stored in the ROM 920. The RAM 922 stores data necessary for control, and stores the peak-peak value PEAK_l and the dc offset, the measured peak-peak value PEAK_c, the dc offset, and the like set in the read-in operation.

Further, it should be understood that the servo controller 914 and the driver 916 can perform focus servo, tracking servo, and spindle servo, which are not shown in detail.

In the focus control operation, the controller 912 measures the dc offset of the focus error signal provided by the RF amplifier 906, compares it with the dc offset of the focus error signal set in the read-in operation, and according to the result, the servo controller Adjust the focus servo gain of 914.

In the double speed control operation, the controller 912 controls the servo controller 914 to rotate the disk 902 according to a set double speed, detect a dc offset of a focus error signal at a current position of the pickup unit 902, and If the dc offset of the detected focus error signal is less than a predetermined reference value Vref, the disk 902 is rotated at a set double speed. If the dc offset of the detected focus error signal is greater than a predetermined reference value Vref, the gain of the focus servo is increased. The disk 902 is rotated at the set speed.

As described above, according to the focus servo control method according to the present invention, if the magnitude of the surface vibration of the disk is detected by the magnitude of the DC offset of the focus error signal, and the surface vibration has a negative effect on the RF signal, By changing the gain of the focus servo to suppress the influence of vibration, it has the effect of enabling a stable recording / reproducing operation.

On the other hand, according to the speed control method according to the invention it is possible to control the speed more stably by suppressing the influence of the disk vibration.

Claims (13)

In the focus servo control method of an optical disc recording and reproducing apparatus, Detecting a dc offset of the focus error signal at the current position of the pickup; And And changing a gain of a focus servo when a dc offset of the detected focus error signal is greater than a predetermined reference value Vref. The method of claim 2, And comparing the difference between the dc offset of the focus error signal measured at the inner circumference of the disk and the dc offset of the focus error signal at the current position with a predetermined reference value Vref. The method of claim 1, A focus control method comprising adjusting a gain of a frequency band corresponding to a surface vibration component. In the focus servo control method of an optical disc recording and reproducing apparatus, Rotating the optical disk at a predetermined speed; Detecting a dc offset of the focus error signal at the current position of the pickup; Rotating the disc at a set double speed if the dc offset of the detected focus error signal is less than a predetermined reference value Vref; And And changing the gain of the focus servo if the dc offset of the detected focus error signal is greater than the predetermined reference value Vref, and rotating the disc at the set double speed. The method of claim 4, wherein Detecting the peak-peak value of the focus error signal at the current position of the pickup; And And rotating the disc at a lower speed than the set double speed if the peak-peak value of the detected focus error signal is greater than the peak-peak value of the focus error signal set at the inner circumference of the disc. The method of claim 4, wherein And comparing the difference between the dc offset of the focus error signal measured at the inner circumference of the disk and the dc offset of the focus error signal at the current position with a predetermined reference value Vref. The method of claim 4, wherein A focus control method comprising adjusting a gain of a frequency band corresponding to a surface vibration component. A pickup unit irradiating a laser beam to the disk, receiving a laser beam reflected from the disk, and outputting an RF signal in an analog form corresponding to the amount of light of the received laser beam; An RF amplifying unit amplifying and outputting an RF signal provided by the pickup unit with a predetermined amplification, and generating a focus error signal necessary for servo control from the RF signal; A servo controller which controls the focus servo of the pickup unit in response to a focus error signal provided by the RF amplifier unit; And It includes a control unit for controlling the above components, Here, the control unit detects a dc offset of the focus error signal at the current position of the pickup unit, and controls the gain of the servo control unit if the dc offset of the detected focus error signal is greater than a predetermined reference value Vref. Optical disc recording / playback device. The method of claim 7, wherein The controller compares a difference between the dc offset of the focus error signal measured at the inner circumference of the disc and the dc offset of the focus error signal at the current position with a predetermined reference value Vref, and controls the gain of the servo controller according to the result. An optical disc recording / reproducing apparatus. The method of claim 7, wherein And the control unit adjusts the gain of the frequency band corresponding to the surface vibration component in the servo control unit. A pickup unit irradiating a laser beam to the disk, receiving a laser beam reflected from the disk, and outputting an RF signal in an analog form corresponding to the amount of light of the received laser beam; An RF amplifying unit amplifying and outputting an RF signal provided by the pickup unit with a predetermined amplification, and generating a focus error signal necessary for servo control from the RF signal; A servo controller which controls the focus servo and the spindle servo of the pickup unit in response to a focus error signal provided by the RF amplifier; And It includes a control unit for controlling the above components, Here, the control unit controls the servo control unit to rotate the disk according to the set double speed, detect the dc offset of the focus error signal at the current position of the pickup unit, the dc offset of the detected focus error signal is a predetermined reference value Vref If smaller, rotate the disc at the set double speed, and if the dc offset of the detected focus error signal is greater than the predetermined reference value Vref, change the gain of the focus servo and rotate the disc at the set double speed. Device. The method of claim 11, The control unit detects the peak-peak value of the focus error signal at the current position of the pickup unit, and sets the set speed if the peak-peak value of the detected focus error signal is larger than the peak-peak value of the focus error signal set in the inner circumference of the disc. An optical disc recording / reproducing apparatus, wherein the disc is rotated at a lower speed. The method of claim 11, And the control unit compares a difference between the dc offset of the focus error signal measured at the inner circumference of the disc and the dc offset of the focus error signal at the current position with a predetermined reference value Vref.