KR20010001209A - Method for tilt controlling - Google Patents

Abstract

PURPOSE: A method for controlling tilts is provided to detect tilts from a level size and a level change of a tracking error signal generated in a free-running state, and to control the tilt to minimize the level change while a level of the tracking error signal becomes maximum, thereby stably and exactly detecting the tilt in an optical disk. CONSTITUTION: An optical pickup(106) is installed according to a guide rail(109) on a deck base(105), to make the optical pickup(106) slide down. A turn table(103) rotates a disk(101) as being rotated according to a driving of a spindle motor(104) for generating a driving power. The turn table(103) axially bonds to the spindle motor(104). A tilt controlling motor(108) is attached to the deck base(105), to generate a driving power for controlling a tilt. A tilt controller(107) axially bonds to the tilt controlling motor(108), to receive the driving power to make the tilt controlling motor(108) rotated. A tracking error(TE) envelop detector(110), a tilt error generator(111), and a tilt driver(112) are sequentially connected to the optical pickup(106). The TE envelop detector(110) detects an envelope of a tracking error signal. The tilt error generator(111) detects tilts from a level change and a level size of the envelope, and generates a tilt error corresponding to the amount of the detected tilts. The tilt driver(112) generates a tilt driving signal in proportion to the tilt error, and outputs the tilt driving signal to the tilt controlling motor(108). A clamp(102) clamps the disk(101) inserted into the turn table(103).

Description

Tilt control method

The present invention relates to an optical record carrier system, and more particularly, to a method of detecting and compensating tilt of an optical record carrier.

In general, an optical recording medium system, that is, an optical disc recording and reproducing apparatus, uses an optical disc such as a compact disc (CD), a digital versatile disc (DVD), etc. as a recording medium to reproduce data recorded on the disc, or It is a device for recording.

At this time, the optical disk may be distorted during the injection and curing of the resin in the manufacturing process, which may cause eccentricity 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.

For this reason, since it is difficult to read exactly the signal of the desired track accurately, the CD and DVD system sets the standard for this deviation amount, and tracking servo is performed so that the light beam can always follow the desired track even if such an 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 or the optical pickup body in the radial direction to correct the position of the beam so that the track can be accurately followed.

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 bent or the turntable is inclined. This may also occur due to mechanical problems such as errors when mounting the disk to the spindle motor. That is, the focusing and tracking do not exactly match vertically, but are distorted. In this manner, the disk is tilted at an arbitrary angle without being perpendicular to the optical axis.

1A to 1C illustrate various examples of the tilt, which are axially coupled to the spindle motor 104 generating a driving force and rotating the disk 101 while being driven by the driving force of the spindle motor 104. 103 and a clamp 102 for clamping the disk 101 seated on the turntable 103 are shown.

1A and 1B show a case in which the turntable 103 is tilted at an arbitrary angle (θ, θ ') with respect to the optical axis, and a tilt occurs. FIG. 1C shows that the turntable 103 is normal, but the disk has a normal angle with respect to the optical axis. It shows the case where the tilt occurred by tilting at an arbitrary angle θ ″.

2 (a) to 2 (c) show examples of the tracking error signal detected at this time, and are cases detected in the free running state.

Here, when the tracking servo is turned off and only the focus servo is turned on, when the optical pickup is fixed and only the disk is rotated, the tracking error signal is detected by the eccentric amount of the disk. This is called free running.

That is, when the defocus and detrack offsets are adjusted so that the tracking error signal is well detected in the tilt 0 (mechanical 0) state, the tracking error signal has the largest level Vpp as shown in FIG. Very few, for example, are flat.

By the way, when the turntable 103 is inclined at an arbitrary angle with the optical axis as shown in FIG. 1A or 1B because foreign matter or the like is caught in the turntable 103, the level Vpp of the tracking error signal is also shown in FIG. As they become smaller, their shape becomes jang-gu. That is, when the turntable 103 is inclined at an angle with respect to the optical axis, the envelope of the tracking error signal is distorted in one rotation period. This occurs because the inclination angle of the turntable 103 changes in one rotation period, so that the optical axis incident on the disk changes.

If it is assumed that the turntable is normal but the tilt is caused by the cause of the disk, only the level Vpp of the tracking error signal is reduced and the shape is flat as shown in FIG.

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 (especially DVD-RAMs) where the track pitch is narrower as optical applications such as optical discs become more dense, the radial tilt margin for jitter is small, so that even if a little tilt occurs, i.e., even when the disc is tilted slightly, There is a detrack that goes over to the side track, where tracking servo is not enough. That is, even if the beam is moved to the next track by tilt, if the beam is in the center of the track, the tracking servo can determine that the track is accurately tracked.

In this case, data cannot be read correctly during playback, and data cannot be recorded accurately on the track during recording, and thus double distortion occurs when the recorded data is played back.

Therefore, the conventional method for solving the above-mentioned tilt is a method of detecting the tilt of the disk by setting a dedicated tilt sensor for detecting the tilt in the pickup, for example, a tilt-only light receiving element, and the twisted tilt angle of the turntable and the micrometer. Likewise, there are methods for adjusting depending on the mechanical measuring device.

However, the above-described methods have a problem that the efficiency of the set is very large while the size of the set is large, and the cost increases because it takes a long time to adjust.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a tilt control method for detecting and compensating the tilt by the level change of the tracking error signal.

1A to 1C are front views showing examples of general tilt generation

(A) to (c) is a waveform diagram showing the change in the tracking error signal according to the tilt

3 is a block diagram of an apparatus for tilt control according to the present invention;

Explanation of symbols for main parts of the drawings

101: optical disk 102: clamp

103: turntable 104: spindle motor

105: deck base 106: optical pickup

107: tilt adjuster 108: tilt adjustment motor

109: guide rail

110: tracking error signal envelope detector

111: tilt error generating unit 112: tilt driving unit

The tilt control method according to the present invention for achieving the above object, the step of obtaining the tracking error signal at the point by rotating the optical disc at a specific point of the optical recording medium, such as an optical disc, the tracking obtained at the step And performing tilt servo by detecting the tilt from the level of the error signal.

The tracking error signal of the above step may be a tracking error signal detected by rotating the optical recording medium with the tracking servo off and only the focus servo on at the corresponding point.

In the tilt servo step, the tilt servo is performed such that the level of the tracking error signal is maximized.

In the tilt servo step, the tilt servo is performed such that the level change of the tracking error signal is minimized.

The present invention is to detect the tilt from the tracking error signal generated during the free running, and to adjust the tilt so that the level change is minimized while the level of the tracking error signal is maximum.

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 in detail with reference to the accompanying drawings.

3 is a block diagram illustrating a device for performing tilt adjustment of the optical recording medium according to the present invention. The deck base 105 is provided with an optical pickup 106 so as to be slidable along the guide rail 109 and has a driving force. The turntable 103 for rotating the disk 101 while rotating in accordance with the drive of the spindle motor 104 for generating a shaft is axially coupled to the spindle motor 104 is installed. In addition, a tilt adjusting motor 108 is attached to the deck base 105 to generate a driving force for tilt adjustment, and the tilt adjusting motor 108 is rotated by a driving force of the tilt adjusting motor 108 to the tilt adjusting motor 108. 107 is condensed. The optical pickup 106 includes a TE envelope detector 110 for detecting an envelope of a tracking error signal TE, a tilt detected from a level change and magnitude of an envelope of the tracking error signal, and corresponds to a detected amount of tilt. The tilt error generating unit 111 generating a tilt error and the tilt driving unit 112 generating a tilt driving signal proportional to the tilt error and outputting the tilt driving signal to the tilt adjusting motor 108 are sequentially connected. Unexplained 102 is a clamp for clamping the disk 101 seated on the turntable 103.

In the present invention configured as described above, the tilt can be detected by the level (Vpp) of the tracking error signal during free running when only the focus servo is turned on while the focus and tracking offset are fixed and the tracking servo is turned off. This is because the tracking error signal detected during free running is highly influenced by the tilt.

To this end, first, the focus servo is turned on at the designated point on the disk and the tracking servo is turned off to drive the spindle motor 104 to rotate the turntable 103 so that the disk 101 rotates together. At this time, if the optical pickup 106 is fixed without moving to the inside or the outside of the disc 101, a tracking error signal is generated by the amount of the eccentricity of the disc 101.

That is, the TE envelope detecting unit 110 generates a tracking error signal from an electrical signal output in proportion to the amount of reflected light from the photo detector in the optical pickup 106 at the time of free running, and then envelopes the envelope of the tracking error signal. Detect.

At this time, the tilt error generator 111 detects the tilt by checking the change and the magnitude of the level Vpp of the tracking error signal from the envelope of the tracking error signal.

If the level change of the tracking error signal is long and the level is small as shown in (b) of FIG. 2, it is determined that a tilt has occurred due to an abnormality of the deck, that is, the turntable 103, and the If the level change is flat as shown in Fig. 2 (c) but the level is small, it is determined that the tilt has occurred due to the abnormality of the disc 101. Then, the tilt amount corresponding to the degree of inclination of the turntable 103 or the degree of warp of the disk 101 is obtained from the magnitude and the change of the level Vpp and outputted to the tilt driver 112.

The tilt driver 112 generates a drive signal to move the tilt adjusting motor 108 by the tilt amount and outputs the driving signal to the tilt adjusting motor 108 attached to the deck base 105.

The tilt adjusting motor 108 is driven forward and backward according to the driving signal proportional to the tilt amount, and the driving force rotates the tilt adjuster 107 axially coupled to the tilt adjusting motor 108 in the forward and reverse directions. .

In this case, the tilt adjuster 107 may use a cam as an example, and the tilt adjuster 107 has an inclined surface that is upward (or downward) from one circumferential surface to the other circumferential surface, so that the tilt adjuster 107 rotates forward and backward. The optical pickup 102 provided on the guide rail 109 moves up and down. In other words, the distance between the disc 101 and the pickup 106 is closer or farther away.

Accordingly, the tilt adjustment motor 108 is controlled by the tilt driver 112 until the level of the level Vpp becomes the maximum while the level change of the tracking error signal is almost not as shown in FIG. That is, the tilt adjuster 107 is rotated forward or reverse so that the optical axis irradiated from the optical pickup 106 to the disk 101 is perpendicular to the disk 101. At this time, not only the tilt by the disk 101 or the turntable 103, but also the tilt that may occur from the spindle, the pickup itself, or the like may be adjusted in the above-described manner.

Here, the abnormality of the turntable 103 can be easily determined by observing the envelope of the tracking error signal using, for example, a glass disc without tilt as a measuring disk. In this case, if it is determined that there is an abnormality, the tilt may be adjusted by the above-described method, or it may be solved by removing foreign matters and the like caught on the turntable.

On the other hand, the present invention can make the tilted track of the disc by detecting the tilt in the above-described way at a plurality of points on the disc, and can estimate the overall tilt of the disc from this.

In addition, the present invention stores the amount of tilt obtained at each position by the above-described method and if the tilt is adjusted in a direction in which the stored tilt amount is decreased at the corresponding recording and reproducing point during actual data recording and reproducing, the tilt is separately detected at that position. No time is needed. This eventually stabilizes the servo quickly and enables real time recording.

As described above, the present invention can detect and adjust the amount of tilt so that the optical axis and the disk surface are perpendicular to each other using the above-described method when performing tilt adjustment or servo.

In addition, although the present invention has been described as an embodiment during free running, the tilt can be detected and adjusted by the above-described method during traverse or recording / playback.

As described above, according to the tilt control method of the optical recording medium according to the present invention, the tilt is detected from the level magnitude and change of the tracking error signal generated in the free running state, and the level of the tracking error signal is maximized. By adjusting the tilt to minimize the change, it is possible to detect and compensate the tilt stably and accurately in a high density optical disk without using a separate light receiving element or a mechanical measuring device. In addition, there is an effect of preventing the deterioration of the data due to the tilt during recording and playback, and prevent the detrack due to the tilt to operate the system stably. In particular, by using a glass disc or the like without a tilt as a measuring disk, it is possible to easily determine the abnormality of the turntable from the tracking error signal detected at this time.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (6)

Rotating the optical record carrier at a specific point of the optical record carrier to obtain a tracking error signal at that point; And detecting tilt from the level of the tracking error signal obtained in the above step, and performing a tilt servo. The method of claim 1, The tracking error signal of the step And a tracking error signal detected by rotating the optical recording medium in a state where the tracking servo is turned off and only the focus servo is turned on at the corresponding point. The method of claim 1, wherein the tilt servo step is And a tilt servo so that the level of the tracking error signal is maximized. The method of claim 1, wherein the tilt servo step is And a tilt servo so that the level change of the tracking error signal is minimized. The method of claim 1, wherein the tilt servo step is A tilt control method characterized by detecting the tilt amount of the entire optical recording medium from the tilt amount obtained at each corresponding point. The method of claim 5, wherein the tilt servo step is A tilt control method comprising storing a tilt amount of an entire optical recording medium and performing a tilt servo in a direction in which the tilt amount decreases at a corresponding recording / reproducing point during data recording and reproducing.