KR20020039505A - Tilt controlling method and apparatus - Google Patents

Abstract

PURPOSE: A method and a device for controlling a tilt are provided to start the tilt control from a position in which RF(Radio Frequency) signals become maximum through a step of initializing a tilt of an optical recording medium, as the position has a most appropriate tilt, and to differentiate an RF envelope value to decide a tilt control direction. CONSTITUTION: A system is run and initialized(51,52). Whether a disk exists is decided. If exists, focus servo is performed and initialization values of each component of a system are changed and set according to the discriminated disk. And if a disk does not exist, disk insertion is waited(53,54,55). When performing focus servo, initialization and the focus are turned 'on'(56,57). Tracking offset and balance are performed for stable tracking servo(58,59). A tilt driver is wobbled for the locus of a tilt driving control amount wobbled when an envelope of an RF value becomes peak. And a central voltage of the locus during one rotation is detected to adjust offset for a tilt error(60). A control window signal is output and the tilt servo becomes 'on'(61,62). A value differentiating the RF envelope value becomes a minus phase for a control phase having a maximum RF envelope value, and becomes a plus phase for an inversed-phase control of the RF envelope(63). When seeking is performed, the tilt and tracking servo are turned off and a sled is moved to a desired position, then the tilt and tracking servo are turned on(65,66,67).

Description

Tilt controlling method and apparatus

The present invention relates to a tilt control method and apparatus for a high-density optical recording medium system. In particular, the tilt control is started at this point because the tilt is best at the point where the RF radio frequency signal is maximized through the optical recording medium tilt initialization process. A tilt control method and apparatus for differentiating an RF envelope value to determine a tilt control direction.

In general, optical recording media are classified into three types, such as read-only ROM, write-once worm type, and rewritable rewritable type. Lose.

The ROM type optical recording medium may include a compact disc read only memory (CD-ROM) and a digital versatile disc read only memory (DVD-ROM), and a worm type optical recording medium may be written once. Recordable Compact Discs (CD-R) and Recordable Digital Versatile Discs (DVD-R).

In addition, freely rewritable discs include a rewritable compact disc (CD-RW) and a rewritable digital versatile disc (DVD-RW, DVD-RAM).

The above-described rewritable optical recording medium, such as an optical disc, has a signal track having a structure of land and groove, so that tracking control can be performed even on a blank disc in which no information signal is recorded. In order to increase the recording density, information signals are recorded on the tracks of the hills and valleys respectively.

Further, the wavelength of the laser light of the optical pickup for recording / reproducing is shortened, and the numerical aperture of the objective lens for condensing is increased to reduce the size of the light beam for recording and reproducing.

In addition, in high density optical discs, the distance between signal tracks, that is, the signal track pitch, is reduced in order to increase the recording density.

At this time, the optical disk may be warped during the injection and curing of the resin in the manufacturing process, and this may cause eccentricity and disk tilt even if the center hole is drilled. Further, even if the disc track is accurately recorded in a spiral shape at a pitch of a predetermined standard, an eccentricity is generated because the center hole is varied. Thus, the disk rotates with eccentricity, so it is difficult for the central axis of the motor and the center of these tracks to completely coincide.

Therefore, since it is difficult to read exactly the signal of the desired track accurately, the CD and DVD system sets the standard for this misalignment amount, and the tracking servo is performed so that the light beam can always follow the desired track even if such eccentricity occurs.

That is, the tracking servo generates an electric signal corresponding to the beam trace state and based on the signal, moves the objective lens and the optical pickup main body in the radial direction to correct the position of the beam to accurately track the track.

On the other hand, when the beam deviates from the track, not only the eccentricity of the disc described above but also the case where the disc is inclined. This can occur due to mechanical problems such as errors when mounting the disk to the spindle motor. In other words, the focusing and tracking do not exactly match vertically. In this way, the disk is tilted.

This tilt was not a big problem for CDs with large track pitches because of their wide track pitch. Here, the tilt margin is an amount that can be corrected even if the disk is inclined to some extent. However, in DVDs whose track pitch is narrowed due to high density, the tilt margin is small, so even if a little tilt occurs, that is, the disc tilts slightly, the beam affects the next track. In this case, the tracking servo is not enough.

In other words, if the beam crosses the track, it is determined that the track does not follow the track center even if the beam is in the center of the track. Therefore, tracking servos cannot track tracks accurately.

In this case, data cannot be read correctly during reproduction, and since the data cannot be recorded accurately on the track during recording, double distortion occurs when the recorded data is reproduced.

Therefore, as a method for solving the above-mentioned tilt problem, there is a dedicated tilt sensor for detecting the tilt. For example, there is a method of detecting the tilt of the disk by setting a tilt-only light receiving element separately. However, the above method suffers from a problem of low efficiency and large set size.

The DVD-RAM rewritable data zone has a header field, and each header field has a variable frequency oscillator (VFO) area for generating a reference clock to synchronize the read channel's bit synchronization. For example, there is a method of controlling the tilt by detecting the tracking error signal and detecting the symmetry of the headers 1,2 and 3,4. However, if there is no header in each sector of the data zone, the tilt cannot be detected in this way. There was no.

Therefore, the present invention obtains the tilt trajectory, which is the RF Max. During one rotation, by using the point that the RF envelope is maximized when the disk and the objective lens are parallel, that is, the tilt is not obtained, and the center potential of the trajectory is obtained. Is set to the tilt control reference voltage and when the RF envelope is in phase with the controller's condition, that is, when the derivative value of the RF envelope becomes the desired phase in the tilt window signal, the tilt control is started to always maximize the RF envelope. The present invention relates to a method and apparatus for controlling tilt.

1 is a block diagram illustrating an optical disk for tilt control according to the present invention.

2A is a waveform diagram illustrating an envelope value of an RF value generated by an optical pickup unit;

2b is a comparative potential for generating a control window from RF Env.

Figure 2c is a waveform showing the time when the control window signal for starting to control the tilt when the RF Env. Value is greater than the comparison voltage

FIG. 2D is a waveform output by the differentiator of the RF envelope value of FIG. 2A and is a waveform showing a direction for controlling tilt. FIG.

3 is a waveform illustrating a tilt control waveform and an RF envelope waveform for tilt wobbling and a control amount required for one cycle of tilt control.

Figure 4a is a waveform showing the envelope value of the RF value for each tilt

FIG. 4B is a graph showing a value obtained by differentiating an RF envelope value according to the tilt of 4A by differentiation and a tilt control direction

5 is an antiphase graph of 4a and 4b.

6 is a detailed flowchart for controlling the tilt of the present invention.

Explanation of symbols for main parts of the drawings

11 optical pickup 12 RF generator

13: RF envelope detector 14: peak window (Peak Window)

15: servo control unit 15a: differentiator

15b: Tilt control unit 16: Tilt drive unit

The tilt control apparatus of the present invention includes an RF generator for generating an RF signal from an electrical signal output from an optical pickup unit, an RF envelope detector for detecting an envelope of the RF signal, and a window signal according to the detected RF envelope value. And a tilt controller for controlling the tilt driver according to the signal of the differentiator and the window unit, and a differentiator for differentiating the detected RF envelope value.

The tilt control method of the present invention comprises the steps of wobbling the tilt driver by a predetermined frequency; Detecting an RF envelope value of the RF high frequency signal output from the optical pickup; Obtaining a tilt control trajectory of the point at which the RF value is the maximum and adjusting and initializing an obcept of the tilt controller; Generating a signal for operating the tilt servo to control the tilt.

In addition, the present invention comprises the steps of wobbling the tilt driver by a predetermined frequency; Detecting an envelope value of the maximum value of the RF high frequency signal output from the optical pickup; And differentially outputting the envelope value to the tilt controller.

In addition, the present invention is characterized by setting the trajectory for controlling the tilt by averaging the maximum / minimum value of the RF high-frequency signal, it characterized in that the control to the direction in which the RF value is the maximum.

In the present invention, the tilt control is characterized in that the tilt control direction is determined according to the derivative value of the RF envelope value of each point to maximize the RF envelope.

In addition, the present invention generates a control window signal for controlling the tilt when the RF value is the maximum, the derivative value of the RF envelope maximum value state is characterized in that 0

In addition, the present invention is characterized in that the RF envelope is controlled to have a positive phase, i.e., the maximum, and the control phase when the envelope value has the maximum value, i.e., the slope of the derivative value is a negative (-) phase.

In addition, the present invention is characterized in that the RF envelope is controlled to have a positive phase, that is, a maximum, and the control phase, that is, the slope of the derivative value, when the envelope value has a minimum value is a positive phase.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

First, FIG. 1 is a block diagram of an optical disc for tilt control according to the present invention, in which an optical pickup unit 11 for recording and reproducing information on an optical disc and an RF high frequency signal are generated from an electrical signal output from the optical pickup unit. An RF generator 12, an RF envelope detector 13 for detecting the envelope of the RF high frequency signal, a peak window 14 for outputting a control window signal when the RF value is maximum, and the detected RF A servo control section 15 for generating a signal for controlling the servo section of the optical system by an envelope (RF env.) And an inverse RF envelope (/ RF env.) And a control window signal of the peak window section, and a tilt output from the servo control section. The tilt driver 16 is configured to control the tilt by controlling the optical pickup unit 11 according to the driving signal.

The servo controller 15 may differentiate the RF envelope (RF env.) And the inverse RF envelope (/ RF env.) Values into a differentiator 15a for use in the control direction of the tilt, and the differentiator and the peak window unit 14. Tilt control unit (15b) for controlling the tilt drive unit in accordance with the control window of the).

FIG. 2 illustrates a waveform diagram operating in FIG. 1. Waveform 2a is a waveform of an RF value generated by the optical pickup unit 11 by wobbling the tilt driver 16 at a predetermined frequency through the tilt controller 15b. Waveform showing the envelope value and RF envelope waveform when the control window signal for controlling the tilt is generated when the RF value reaches the maximum value.

2b shows a comparison potential for generating a control window from RF Env.

FIG. 2C illustrates a binary phase clock compared with a comparison potential of the RF envelope value of FIG. 2A. FIG. 2C is a waveform illustrating a time point of generating a control window signal for controlling tilt when the RF Env. Value is greater than or equal to the comparison voltage.

In this figure, the negative phase of the differential signal during the tilt control is the optimum tilt control phase.

FIG. 2D is a waveform showing the direction and control amount of controlling the tilt with the waveform output by the differentiator 15a from the RF envelope value of FIG. 2A.

In this figure, the negative phase of the differential signal during the tilt control is the optimum tilt control phase.

FIG. 3 shows the tilt control waveform and the RF envelope waveform for the tilt wobbling and the trajectory of the tilt error of one cycle (more than one rotation) by the disk isolation and the like.

FIG. 4 shows the tilt size of the focus driver (not shown) under the control of the servo controller 15 to drive the focus actuator (not shown) in the optical pickup unit 11 to reflect the RF value generated by the optical disk. It is a derivative value representing the control amount and control direction according to each tilt value by the change of the positive RF envelope value having a maximum value and the differentiation.

4A shows a positive envelope value of an RF value according to each tilt. When the tilt is twisted in a positive or negative direction based on the maximum point of the RF envelope, the RF envelope becomes smaller.

Figure 4b is an RF envelope value according to the tilt of 4a, it shows that the RF envelope is reduced according to the amount of tilt. That is, the RF envelope decreases as the disk is tilted from 0, which is the center position of the disk's tilt, and the derivative of the RF envelope is a signal having tilt information.

FIG. 5 is a derivative of the output of FIG. 4 converted into a reversed phase and showing a control amount and a control direction according to a change in a positive (+) RF envelope value having a minimum value and a tilt value according to the magnitude of the tilt.

6 is a detailed flowchart of the present invention, which will be described with reference to the above drawings.

Power on the optical record carrier system (DVD) to operate the system and proceed with the initialization process. (Steps 51 and 52).

In other words, the system controller initializes each component to suit the system according to the reset of the controller while power is supplied, and operates according to the firmware (F / W) implemented in the controller. Offset the servo channel's opps. And initialize the initialization element performed without input of the RF signal. For example, the initial diagnosis of the system is performed by initializing the factors related to the sled movement or by positioning the objective lens at the initial position.

Thereafter, the optical pickup unit 11 performs focus and determines the presence or absence of a disk and a disk type, and selects a laser power and a focus servo controller of a laser diode (not shown) in the optical pickup unit and performs a focus servo according to the disk type. After the determination is completed, each part of the system is set by changing the initialization value according to the disc determined. If it is determined that there is no disk, wait for the disk to be inserted. (Steps 53,54,55).

When the focus servo is performed, the initialization and the focus related to the focus are turned on. At this time, the focus focus and the balance are performed to perform the stable focus servo. (Step 56.57).

After the focus servo has stabilized, it is initialized and turned on for tracking.

At this time, tracking tracking and balance are performed to perform stable tracking servo. (Step 58,59).

After the focus servo and tracking servo are stabilized, the process of initializing the tilt is performed. Here, when the disk as the recording medium and the objective lens in the optical pickup unit are aligned without mutual inclination, the RF level reflected from the disk is maximum.

In other words, when the disk is mounted without isolating factor and the tilt is 0, the RF becomes the maximum value and the envelope value of the RF value increases / decreases according to the tilt value (Fig. 4). In the turned-on state, the tilt driver 16 may be wobbed by a predetermined frequency through the tilt controller 15b to perform a trajectory of the tilt drive control amount wobbling at a peak point of the envelope of the RF value for one rotation. It is also possible to carry out during rotation.

During this one revolution, the center voltage of the trajectory is detected to adjust the opposition to the tilt error (step 60, Figs. 4 and 5).

The tilt wobbling method is applied to output a control window signal for controlling the tilt control unit at the peak window units (FIGS. 1 and 14) at the point where the RF value is Max. (FIG. 2C). Thus, the tilt control unit 15b is a tilt driving unit ( 16. The tilt servo for operating 16) is turned on (steps 61 and 62).

Therefore, the tilt is controlled. The control amount and the control direction are waveforms of FIG. 2D obtained by differentiating the RF envelope value of FIG. 2A. In detail, as shown in FIG. 4, when the RF envelope value has the maximum value, the control phase when the RF envelope value is differentiated becomes a negative (-) phase. That is, the RF envelope derivative is controlled to be 0. In addition, as shown in FIG. 5, the control phase in the case of controlling the reverse phase of the RF envelope is a positive phase obtained by differentiating the reverse phase RF envelope value (step 63).

In the case of seek, the tilt and tracking servo are turned off, the sled is moved to a desired position, and the tilt and tracking servo can be turned on (steps 65, 66 and 67).

In this case, the normal servo is always controlled in the direction in which the RF envelope is maximized. After the disk drive is completed, the tracking servo and focusing servo are turned on and the tilt initialization is performed again.

As described above, in the present invention, in the driving of the disc, the tilt driving unit is wobbed by a predetermined frequency through the tilt control unit while the focusing and tracking servo is turned on. The above tilt trajectory is obtained to initialize the tilt control system, and the tilt servo is turned on to determine the tilt control amount and control direction using the detected / differentiated envelope value. Here, the tilt control point outputs a control window signal for controlling the tilt from the peak window unit to the tilt control unit when the RF value is maximum by applying the tilt wobbling method described above.

As described above, according to the tilt control method and apparatus according to the present invention, in driving a disk, while the focusing and tracking servo is turned on, the tilt driving unit is wobbed by a predetermined frequency through a tilt control unit so that an RF value is obtained. Initializing the tilt control system by detecting the tilt trajectory of Max.point more than 1 cycle and determining the tilt control amount and control direction by using the detected / differentiated RF envelope value. It is possible to detect and control the tilt stably and accurately without using it.

Claims (10)

In the optical recording / reproducing apparatus, An RF generator for generating an RF signal from an electrical signal output from the optical pickup unit; An RF envelope detector for detecting an envelope of the RF signal; A window unit generating a window signal according to the detected RF envelope value; A differentiator for differentiating the detected RF envelope values; A tilt control unit including a tilt control unit controlling the tilt driving unit according to the differential and window signal An optical recording medium recording / reproducing apparatus which performs tracking servo and focusing servo by detecting a tracking error signal and a focusing error signal by using an electrical signal of an optical pickup that receives a laser at a designated position of the optical recording medium and then picks up the reflected light. In the tilt control method of, Wobbling the tilt driver by a predetermined frequency; Detecting an RF envelope value of the RF high frequency signal output from the optical pickup; Obtaining a tilt control trajectory of the point at which the RF value is the maximum and adjusting and initializing an obcept of the tilt controller; And generating a signal for operating the tilt servo to control the tilt. 3. The tilt control according to claim 2, wherein the tilt control is set as a trajectory for controlling the tilt by averaging the maximum / minimum value of the tilt control amount of one or more rotations of the maximum peak of the RF high frequency signal and controlling the direction in which the RF value is maximized. Way. An optical recording medium recording / reproducing apparatus which performs tracking servo and focusing servo by detecting a tracking error signal and a focusing error signal by using an electrical signal of an optical pickup that receives a laser at a designated position of the optical recording medium and then picks up the reflected light. In the tilt control method of, Wobbling the tilt driver by a predetermined frequency; Detecting an envelope value of the maximum value of the RF high frequency signal output from the optical pickup; Tilting the envelope value and outputting the derivative to the tilt control unit. The tilt control method according to claim 4, wherein the tilt control direction is determined according to the derivative value of the RF envelope value at each point so that the RF envelope is maximized. 5. The tilt control method according to claim 4, wherein the tilt control is determined according to the derivative value of the RF envelope value at each point so that the RF envelope is maximized. 5. The tilt control method according to claim 4, wherein a control window signal for controlling the tilt is generated when the RF value is maximum, and the derivative value of the RF envelope maximum value state is 0. 5. The tilt control method according to claim 4, wherein when the disk seek is performed, the tilt and tracking servo are turned off, the sled is moved to a desired position, and the tilt and tracking servo are turned on. 5. The tilt control method according to claim 2 or 4, wherein the control phase is controlled so that the RF envelope is in a positive phase, and the control phase when the envelope value has a maximum value is a negative phase. 5. The tilt control method according to claim 2 or 4, wherein the control phase is controlled so that the RF envelope is in a positive phase, and the control phase when the envelope value has a minimum value is a positive phase.