KR20000026833A - Method for detecting tilt - Google Patents

Abstract

PURPOSE: A method for detecting tilt is provided to stably and accurately detect and compensate a tile by detecting amount of tilt using a difference with a reference value and detecting a tilt direction using a focus error signal, and then performing a tilt servo using the tilt amount and the tilt direction. CONSTITUTION: An optical pick-up(101) records and reproduces information to an optical disk(100). A tracking error detecting unit(102) detects a TE(Tracking Error) signal using an electric signal outputted from the optical pick-up(101) and computes a number of the TE signal. A comparator(103) outputs a difference of the number of TE signal and a reference value(ref1). A table(104) receives the output of the comparator(103) and outputs a corresponding tilt amount. A focus error detecting unit(105) detects a FE(Focus Error) signal using an electric signal outputted from the optical pick-up(101). A tile size and direction detecting unit(106) detects a tilt direction using the FE signal and outputs the detected tilt direction and the tile amount outputted from the table(104). A tilt controller(107) revises a tilt using the output of the tile size and direction detecting unit(106).

Description

Tilt detection method

The present invention relates to a high density optical recording medium system, and more particularly to a tilt detection method for detecting the tilt size and direction of the optical recording medium.

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-Rs) and Recordable Digital Versatile Discs (DVD-Rs).

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

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, an information signal is recorded on each track of a mountain and a valley. That is, 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.

On the other hand, such an 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.

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 a 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. That is, the focusing and tracking do not exactly match vertically, but are distorted. 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 that even if only a small tilt occurs, that is, the disc is tilted slightly, the beam passes over to the next track. In this case, the tracking servo is not enough. That is, even if the track is moved to the side track, the tracking servo can determine that the track is correctly tracked if the beam is in the center of the track.

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, there is a method of detecting the tilt of the disk with a dedicated tilt sensor for detecting the tilt in the pickup, for example, a tilt-only light receiving element. However, the above-described method has a problem in that the size of the set becomes large while the efficiency is not very good.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is a tilt amount for a difference between the number of tracking error signals detected while transferring an optical pickup from the inner circumference to the outer circumference when a disk is mounted and a preset reference value. To provide a tilt detection method for detecting using a table.

Another object of the present invention is to provide a tilt detection method for detecting a direction of tilt using a focus error signal.

1 is a block diagram of an optical disk recording / reproducing apparatus for tilt detection according to the present invention.

(A) to (c) is a waveform diagram showing an example of a tracking error signal according to the steady state and the magnitude of the tilt

3 is a diagram illustrating an example of a light detector of the optical pickup of FIG. 1;

Explanation of symbols for main parts of the drawings

100: optical disk 101: optical pickup

102: tracking error detection unit 103: comparator

104: Table 105: Focus error detector

106: tilt size and direction detection unit 107: tilt controller

The tilt detection method according to the present invention for achieving the above object, the step of detecting the number of tracking error signal while transferring the optical pickup from the inner circumference to the outer circumference, the number of the detected tracking error signal and the preset Calculating a difference from a reference value, and applying the calculated difference value to a table to detect a tilt amount.

The amount of tilt corresponding to the difference between the reference value and the number of tracking error signals is pre-mapped in the table.

The tilt amount detecting step may detect a direction of the tilt by using a focus error signal.

Compensating the tilt by performing a tilt servo in the detected tilt amount and the tilt direction.

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.

According to the present invention, the tilt amount of the difference between the reference value and the number of tracking error signals generated during the optical pickup transfer process is pre-mapped to a table, and then the optical pickup is transferred from the inner circumference to the circumferential direction at the initial stage when the disk is mounted. The difference between the tracking error signal and the reference signal is applied to the table to detect the amount of tilt.

FIG. 1 is a block diagram of an optical disk recording / reproducing apparatus according to the present invention for detecting such tilt. An optical disk 100 capable of rewriting data and an optical pickup for recording and reproducing information on the optical disk 100 are shown in FIG. (101), a tracking error detection unit (102) for detecting a tracking error (TE) signal using an electrical signal output from the optical pickup 101, and obtaining the number of the tracking error signals, and the number and reference values of the TE signals ( a comparator 103 for outputting a difference from ref1), a table 104 for receiving the output of the comparator 103 and outputting a corresponding tilt amount, and a focus using an electrical signal output from the optical pickup 101 Focusing error detection unit 105 for detecting an error (FE) signal, the tilt by using the FE signal after detecting the direction of the tilt and the amount of tilt output from the table 104, that is, the amount of tilt It consists of a group, and a direction detector 106, and a tilt controller (107) for correcting the tilt by using the output of the tilt magnitude and direction detecting section 106. The tilt controller 107 is a tilt servo mechanism that corrects tilt by moving the optical pickup or by moving the disk itself.

Here, the optical pickup 101 is provided with a photo detector for detecting the light amount of the beam and converting the light amount into an electrical signal, the optical detector is a signal track direction and radial direction of the optical disk 100 as shown in FIG. In this case, it is possible to configure four specific photodetectors (PDA, PDB, PDC, PDD).

In the present invention configured as described above, when the optical disk recording / reproducing apparatus is initially turned on, the optical pickup 101 is transferred from the inner circumference to the outer circumferential direction of the optical disk 100. At this time, the laser light emitted from the laser diode of the optical pickup 101 is placed on the signal track of the rotating optical disk 100, where the reflected light is incident on the photo detector. Therefore, the tracking error signal according to the movement of the optical pickup 101 can be detected.

If the photo detector is configured as shown in FIG. 3, the photo detector transmits the electrical signals a, b, c, and d to the TE detector 102 in proportion to the amount of light obtained from each of the photo detector elements PDA, PDB, PDC, and PDD. Output to FE detection unit 105.

The TE detector 102 detects a TE signal by (a + d)-(b + c) the electrical signals a, b, c, and d that are input, and then uses a counter (not shown). The number of tracking error signals from the inner circumference to the outer circumference of the disc 100 is obtained and output to the comparator 103. The comparator 103 calculates a difference between the number of input TE signals and a preset reference value ref1, and then outputs the difference value to the table 104. The table 104 outputs a tilt amount corresponding to the difference value. .

Here, the reference value ref1 may be the number of tracking error signals from the inner circumference to the outer circumference of the optical disc 100 when there is no tilt, that is, in a normal state.

At this time, there is a tilt of the optical disk or the disk itself, and the larger the tilt, that is, the larger the angle at which the disk is bent, the narrower the width of the tracking error signal is and the number of tracking error signals increases.

FIG. 2A shows an example of a tracking error signal in a steady state, and FIG. 2B is a tracking error signal when a tilt has occurred, which is narrower than when the width B of the tracking error signal is in the steady state A. FIG. FIG. 2C shows the tracking error signal C detected when the bending angle of the disc is larger than that of FIG. 2B, and is narrower than the width B of the tracking error signal of FIG. 2B.

Therefore, if the tilt amounts according to the difference values between the reference value ref1 and the number of detected tracking error signals are pre-mapped to the table and the difference value output from the comparator 103 is applied to the table 104, the tilt amount is immediately obtained. Can be obtained.

In addition, the FE detector 105 detects the FE signal by (a + c)-(b + d) the electrical signals (a, b, c, d) inputted and outputs the tilt magnitude and direction detector 106. do.

The tilt magnitude and direction detector 106 obtains the direction of tilt using the FE signal and outputs the tilt direction to the tilt controller 107 together with the amount of tilt read from the table 104.

That is, in the normal case, the objective lens of the optical pickup is precisely focused on the reflective surface of the disk. However, the distance between the disc and the optical pickup is continuously changed due to the tilt, eccentricity, etc. of the disc, and the focus is also released. In general, when the reflected light is emitted from the disk, the objective lens becomes a parallel beam when the focal point coincides with the disk reflecting surface, a diverging beam when it is close to the lens, and a focused beam when it is far away.

If it is assumed that the FE signal is detected by using the photodetector as shown in FIG. 3, when the focus is correctly obtained, the beam shape becomes circular and the output of the FE detector 105 becomes '0', When the distance between the objective lens and the disk is close, the shape of the beam becomes elliptical and the output of the FE detector 105 becomes '+', and in the far case, '-'. Therefore, looking at the output of the FE detector 105, it can be seen whether the direction of the tilt, that is, the disk is bent downward or upward than when the disk is in a normal state. If the disc is bent downward, the tilt can be compensated by the amount of tilt in the upward direction.

Therefore, the tilt controller 107 controls the tilt by moving the disk or moving the optical pickup by the amount of tilt in the + or-direction.

As described above, the present invention performs the recording / reproducing of data after correcting the tilt once.

As described above, according to the tilt detection method according to the present invention, when the optical disc recording / reproducing apparatus is initially turned on after the tilt amounts according to the difference between the reference value and the number of detected tracking error signals are pre-mapped, the optical pickup is performed. Detects the number of tracking error signals while moving from the inner circumference to the outer circumferential direction, and applies the difference from the preset reference value to the table to detect the amount of tilt, and detects the direction of tilt using the focus error signal. By performing the tilt servo in the tilt amount and the tilt direction, the tilt can be detected and compensated stably and accurately without using a separate light receiving element in the high density optical disk.

Claims (5)

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 detection method of, Detecting the number of tracking error signals while transferring the optical pickup from the inner circumference to the outer circumferential direction; Calculating a difference between the number of the detected tracking error signals and a preset reference value; And detecting the tilt amount by applying the calculated difference value to a table. The method of claim 1, The reference value of the calculation step is And a number of tracking error signals in a steady state. The method of claim 1, And a tilt amount corresponding to a difference value between a reference value and a number of tracking error signals according to a plurality of tilt angles is pre-mapped. The method of claim 1, The tilt amount detection step And a tilt detection direction using the focus error signal. The method of claim 1, The tilt amount detection step And compensating for the tilt by performing a tilt servo in the detected tilt amount and the tilt direction.