KR20020028003A - Method for compensating a error swerved from optical axis in optical pick up - Google Patents

Abstract

PURPOSE: A method for compensating the distortion of an optical axis is provided to adjust a focus lens in a horizontal direction, when a beam spot emitted from a light emitting element such as a laser diode and reflected by a recording surface of an optical disk is formed in a position out of an X-Y axis from a center of a light collecting element such as a photo diode. CONSTITUTION: When an optical disk is stably mounted(S10), a microcomputer moves a focus lens to the optical disk from an initial set position(S12) and detects a signal level and a waveform of an FE(Focus Error) signal(S14). Whether the signal levels and waveform in a high section and in a low section of the FE signal are symmetric each other is decided(S16). If so, a normal state is decided(S30). If not symmetric, whether the signal level and waveform of the FE signal in the high section is smaller is decided(S18). If so, the beam spot is decided to be improperly formed in a B or D area of a 4-divided light collecting element, out of X-Y axis(S20). A track offset voltage is supplied to an actuator to move the beam spot formed in the B area to a central position(S22). Whether the signal level and waveform in a high section and in a low section of the FE signal are symmetric each other is decided(S24). If not symmetric, the track offset voltage is variably supplied to move the beam spot formed in a D area to a central position(S26). And normal focusing and tracking operations are performed(S28).

Description

Method for compensating a error swerved from optical axis in optical pick up}

The present invention relates to an optical axis distortion compensation method in an optical pickup, and more particularly, a beam spot emitted from a light emitting element such as a laser diode and reflected by the recording surface of the optical disc is shifted from the center position of the light receiving element to the XY axis. The present invention relates to an optical axis distortion compensation method in an optical pickup for compensating for optical axis distortion.

First, FIG. 1 shows a configuration of a general optical disc device, which includes an optical pickup for reading out a signal recorded on an optical disc 1 such as a CD or a digital versatile disc (DVD). (P / U) (2); A filter forming unit (3) for outputting an RF signal, a focus error signal, and a tracking error signal by adding or subtracting an electric signal read out by the optical pickup (2); A digital signal processor (DSP) 4 for restoring the filtered RF signal to digital data to process a reproduction signal; Sled motor (9) for moving the optical pickup (2); A spindle motor 10 for rotating the optical disc 1; A driver (8) for driving rotation by applying a driving voltage to the sled motor (9) and the spindle motor (10); A servo unit 5 which controls the optical pickup 2 and the driver 8; A micom 6 for controlling operations of the servo unit 5 and the digital signal processing unit 4; And a memory 7 for storing data (Data) necessary for the control operation of the microcomputer 6.

On the other hand, the optical pickup 2 includes: a light emitting element 21 such as a laser diode which emits light in order to read out a signal recorded on the recording surface of the optical disc 1; A collimator lens 22 for converting light emitted from the light emitting element into parallel light; A focus lens 24 for condensing the converted parallel light to form a beam spot on a recording surface of the optical disc; A half mirror 23 for transmitting the parallel light converted by the collimator lens and reflecting the reflected light passing through the focus lens 24 at a 90 degree angle reflected by the recording surface of the optical disk; And a condenser lens 25 condensing the reflected light reflected by the half mirror at an angle of 90 degrees to form a beam spot on the light receiving element 26 such as a photo diode. Servo control operation performed in a general optical disk device is as follows.

First, when the optical disc 1 is inserted and seated in a tray (not shown) provided in the optical disc apparatus, the optical disc 1 is clamped by a clamper (not shown) and then supplied from the driver 8. The spindle motor 10 is rotated at a constant speed in accordance with the driving voltage to rotate the optical disc 1 at a constant speed. In the optical pickup 2, as shown in FIG. 2, the optical disc 1 In order to read the signal recorded on the recording surface of the light emitting element 21 such as a laser diode provided in the optical pickup 2, the light is emitted.

Accordingly, the beam spot formed and reflected on the recording surface of the optical disk is converted into an electrical signal by the light receiving element 26, and the converted electrical signal is converted into binary by the filter shape section 3. After being converted into a pulse signal, the digital signal processor 4 is further processed into digital data.

On the other hand, in the servo section 5, a track jump operation for largely moving the optical pickup 2 in the transverse direction of the optical disk track, that is, a track search (for large traversal and movement of the track of the optical disk 1) A focusing operation of controlling the rotation operation of the sled motor 9 and variably adjusting the vertical position and the horizontal position of the focus lens provided in the optical pickup 2 when the search operation is performed. The tracking operation is controlled, and the beam spot formed in the light receiving element 26 receives the light by physical distortion generated in the process of mounting the optical pickup 2 in an optical disk device such as a disk driver. Optical axis skew may be caused to deviate from the center of the element 26 to the XY axis.

As shown in FIG. 3, the optical axis shift is performed in a specific divided region, for example, A region or B region, deviated from the center of the light receiving element divided into four divisions (A, B, C, D) on the XY axis. It may be formed as a beam spot of an abnormal shape, when the focus lens 4 detects a focus error signal (FE: Focus Error) while moving upward in the direction of the optical disc from a predetermined initial position of focus, that is, the 4 Focus that is the difference signal between the sum of the electric signals converted by the A and C areas of the divided light receiving elements (A + C) and the sum of the electric signals converted by the B and D areas (B + D) When an error signal FE = (A + C)-(B + D) is detected, the focus error signal waveform is detected as an abnormal waveform.

As a result, accurate focusing and tracking operations are prevented from occurring, resulting in a playback error in which a signal recorded on the optical disc cannot be read and reproduced normally, and as a result, it is judged as a bad optical pickup or the XY axis is adjusted. There was a problem that must include a separate adjustment process for the manufacturing process.

Therefore, the present invention was created to solve the above problems, wherein a beam spot emitted from a light emitting element such as a laser diode and reflected by the recording surface of the optical disc is moved from the center position of the light receiving element such as the photodiode to the XY axis. When formed at an off position, the position of the focus lens is variably adjusted in the horizontal direction so that the beam spot is formed at the center position of the light receiving element, so that the physical distortion in the process of mounting the optical pickup in the optical disk device such as a disk driver, etc. It is an object of the present invention to provide a compensation method for optical axis distortion in an optical pickup that can compensate for optical axis displacement caused by the optical pickup.

1 shows a configuration of a general optical disk device,

2 illustrates a configuration of a general optical pickup,

FIG. 3 illustrates waveforms and output levels of the focus error signal FE as the optical axis shifts in a general optical pickup.

4 is a flowchart illustrating an optical axis shift compensation method in an optical pickup according to the present invention;

5 shows values of optical axis error signals PD-XE and PD-YE applied to the present invention.

6 and 7 illustrate an operation flowchart of another embodiment of the optical axis shift compensation method in the optical pickup according to the present invention.

※ Explanation of code for main part of drawing

1: Optical disc 2: Optical pickup (P / U)

3: Filtering part (R / F) 4: Digital signal processing part (DSP)

5: Servo part 6: Micom

7: Memory 8: Driver

9: Sled Motor 10: Spindle Motor

21 light emitting element 22 collimator lens

23: half mirror 24: focus lens

25 condensing lens 26 light receiving element

According to an aspect of the present invention, there is provided a method of adjusting an optical axis distortion in an optical pickup, the method including: detecting a focus error signal according to movement of an optical pickup when an optical disc is mounted; Determining whether a position of a beam spot formed in the light receiving element is formed at a center position based on the waveform or level of the detected focus error signal; And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination.

In addition, the optical axis distortion compensation method in the optical pickup according to the present invention, when the optical disk is mounted, detecting the optical axis error signal according to the optical pickup movement; Determining whether the position of the beam spot formed in the light receiving element is formed at the center position based on the waveform or level of the detected optical axis error signal; And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination.

In addition, the optical axis distortion compensation method in the optical pickup according to the present invention, when mounting the optical disk, the first step of detecting each electric signal photoelectrically converted by the light receiving element divided into a plurality of areas in the optical pickup; Comparing the electric signals for each detected region, and determining whether a position of a beam spot formed in the light receiving element is formed at a center position; And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination.

In addition, the optical axis distortion compensation method in the optical pickup according to the present invention, when mounting the optical disk, while detecting the focus error signal and the optical axis error signal while moving the focus lens in the direction of the optical disk at a predetermined initial lower position in advance Stage 1; If the waveform and signal level of the focus error signal are abnormally detected, determining whether the position of the beam spot formed in the light receiving element is out of the center position based on the optical axis error signal; And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination.

In addition, the optical axis distortion compensation method in the optical pickup according to the present invention, when mounting the optical disk, while moving the focus lens in the direction of the optical disk at a predetermined initial lower position in advance, the focus error signal and a plurality of in the optical pickup Detecting each electric signal photoelectrically converted by the light receiving element divided into regions; If the waveform and signal level of the focus error signal are abnormally detected, determining whether the position of the beam spot formed in the light receiving element is out of the center position based on the electric signal for each region; And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination.

Hereinafter, a preferred embodiment of an optical axis misalignment compensation method in an optical pickup according to the present invention will be described in detail with reference to the accompanying drawings.

First, as described above, when optical axis distortion occurs in the process of mounting the optical pickup 2 in an optical disk device such as a disk driver, by physical torsion or the like, the optical pickup 2 is formed at a position deviated from the center of the light receiving element 26 on the XY axis. The beam spot to be formed is usually mainly formed in the B region and the D region of the light-receiving element 26 divided into four. For example, as shown in FIG. 3, when the beam spot is formed in the B region, The focus error signal waveforms in the high section and the low section are detected as asymmetrical to each other, and the focus error signal level in the high section is detected at an output level lower than the preset reference high level Ref_H. do.

When the beam spot is formed in the A region, the focus error signal waveforms in the focus high section and the low section are detected as asymmetrical to each other, and the focus error signal level in the low section is set in advance to a reference low level ( Ref_L) is detected at an output level higher than that, and based on the waveform and level of the focus error signal detected as described above, a method of compensating for optical axis distortion in the optical pickup will be described in detail.

4 is a flowchart illustrating an optical axis distortion compensation method in the optical pickup according to the present invention. When the optical disk is inserted and seated in an optical disk device such as a disk driver (S10), the microcomputer 6 detects this. After confirming, the servo unit 5 is operated to execute the focus initialization operation. The focus initialization operation, that is, the focus lens 2 is moved upward in the optical disc direction to a predetermined initial lower position (S12). ), The signal level and waveform of the focus error signal FE = (A + C)-(B + D) are detected (S14).

At this time, when the focus error signal waveforms in the high section and the low section are symmetrical with each other (S16), it is determined that the optical axis is in a normal state without distortion (S30), while the signal waveform of the focus error signal is asymmetrical, and the high section is In the case where the focus error signal level and the waveform are smaller than the low section (S18), the beam spot formed in the light receiving element 26 is deviated from the center of the four divided regions by the horizontal XY axis, especially in the clockwise direction. After determining that it is formed incorrectly in the B or D area of the light receiving element 26 divided into A, B, C and D areas (S20), a track offset for moving the focus lens in the horizontal direction (Track Offset) is applied to an actuator (not shown) for moving the focus lens to move the beam spot formed in the B region of the light receiving element to a center position (S22).

Thereafter, when the focus error signal waveforms in the high section and the low section are symmetrical with each other (S24), it is determined that the optical axis is in a normal state without distortion (S30). Meanwhile, when asymmetrically symmetrically, the focus lens is moved in the horizontal direction. By varying the track offset voltage to move, the beam spot formed in the D region of the light receiving element is moved to the center position (S26), and the optical axis shift compensation operation of moving the beam spot formed in the D region of the light receiving element to the center position In this case, the track offset voltage applied to the actuator reads from the memory 9 the track offset voltage which is stored in advance through experiment, or corresponds to the waveform and level of the focus error signal. Can be calculated and applied by a separate arithmetic equation for calculating the track offset voltage. Track offset value is based on the level and the waveform of the focus error signal, and may be stored as a management table stored in the form of a track offset calculation table in advance.

Subsequently, when the optical axis shift compensation operation is performed as described above, a normal focusing operation and a tracking operation are performed (S26), and the signal recorded on the optical disc is read and reproduced normally.

On the other hand, in the process of mounting the optical pickup 2 in an optical disk device such as a disk driver, optical axis distortion occurs due to physical distortion, such that the beam spot formed on the light receiving element 26 is off the center position from the XY axis, for example For example, when a beam spot is formed in the B region of the light-receiving element 26 divided into four, unlike the X-axis error signal, that is, the focus error signal, an electrical signal converted and output from the A and D areas of the light-receiving element divided into four parts. X-axis error signal PD-XE = (A + D)-(B + C), which is the difference signal between the sum (A + D) and the sum (B + C) of the electrical signals converted and output from the B and C areas. ) Is detected as a value smaller than zero, and the sum (A + B) of the electrical signals converted and output from the A and B areas of the light-receiving element divided into four, and the electrical signals converted and output from the C and D areas. The Y-axis error signal (PD-YE = (A + B)-(C + D)), which is the difference signal between the sums (C + D), is greater than zero. It is.

When the beam spot is formed in the D region, the X-axis error signal PD-XE = (A + D)-(B + C) is detected as a value larger than zero, and the Y-axis error signal ( PD-YE = (A + B)-(C + D)) is detected with a value smaller than zero, and based on the detected X-axis and Y-axis error signals, the optical axis in the optical pickup The method of compensating for the distortion is described in detail as follows.

6 is a flowchart illustrating another embodiment of the optical axis distortion compensation method in the optical pickup according to the present invention. When the optical disk is inserted and seated in an optical disk device such as a disk driver (S50), the microcomputer 6 After detecting and confirming the detection, the servo unit 5 is operated to execute the focus initialization operation. The focus initialization operation, that is, the focus lens 2 is moved upward in the optical disc direction at a predetermined initial lower position. (S52), the X-axis error signal (PD-XE = (A + D)-(B + C)) and the Y-axis error signal (PD-YE = (A + B)-(C + D)) It is detected (S54).

At this time, when the X-axis error signal PD-XE and the Y-axis error signal PD-YE have a value of zero (S56), it is determined that the beam spot is normally formed at the center position of the light receiving element (S64). On the other hand, while the general focus and tracking servo operation is performed (S66), the X-axis error signal PD-XE is detected to be smaller than zero, and the Y-axis error signal PD-YE is less than zero. When it is detected with a large value (S58), as described above, after determining that the beam spot is formed incorrectly in the B region of the four-segmented light-receiving element 26, it is necessary to move the position of the focus lens in the horizontal direction. The track offset voltage is applied to an actuator (not shown) for moving the focus lens to move the beam spot formed in the B region of the light receiving element to a center position (S60).

On the other hand, when the X-axis error signal PD-XE is detected with a value greater than zero, and the Y-axis error signal PD-YE is detected with a value less than zero, the light receiving element 26 is divided into four. After determining that the beam spot is formed incorrectly in the area D, the track offset voltage for shifting the position of the focus lens in the horizontal direction is applied to an actuator (not shown) for moving the focus lens. The optical axis distortion compensation operation for moving the beam spot formed in the D region of the center to the center position is performed (S62), and the track offset voltage applied to the actuator is stored in advance through experiments as described above. The track offset voltage which is read out from the memory 9 or calculates a track offset voltage corresponding to the waveform and level magnitude of the focus error signal. Can be applied to calculation, and can also be a track offset value stored in the memory (7), on the basis of the level and the waveform of the focus error signal, stored in the track offset calculation table stored in table form in the pre-administration.

Subsequently, when the optical axis shift compensation operation is performed as described above, a normal focusing operation and a tracking operation are performed (S64), and the signal recorded on the optical disc is read and reproduced normally.

FIG. 7 is a flowchart illustrating another embodiment of the optical axis distortion compensation method in the optical pickup according to the present invention. When the optical disk is inserted and seated in an optical disk device such as a disk driver (S70), the microcomputer 6 ) Detects the signal level and waveform of the focus error signal FE, the X-axis error signal and the Y-axis error signal while moving the focus lens 2 upward in the optical disk direction to the initial lower position set in advance (S72). (S74) When the waveform of the detected focus error signal is abnormal (S76), that is, when the focus error signal waveforms in the high and low sections are detected as abnormal waveforms that are asymmetric with each other, it is determined that the optical axis is distorted. (S78).

Subsequently, as described above with reference to FIG. 6, when the X-axis error signal PD-XE and the Y-axis error signal PD-YE have a value of zero (S80), the beam spot of the light receiving element While it is determined that it is normally formed at the center position (S88), the general focus and tracking servo operation is performed (S90), while the X-axis error signal PD-XE is detected as a value smaller than zero, and the Y-axis If the error signal PD-YE is detected as having a value greater than zero (S82), it is determined that the beam spot is incorrectly formed in the B region of the four-segmented light receiving element 26, and then the position of the focus lens is changed. The track offset voltage for moving in the horizontal direction is applied to an actuator (not shown) for moving the focus lens to move the beam spot formed in the B region of the light receiving element to the center position (S86).

On the other hand, when the X-axis error signal PD-XE is detected with a value greater than zero, and the Y-axis error signal PD-YE is detected with a value less than zero, the light receiving element 26 is divided into four. After determining that the beam spot is formed incorrectly in the area D, the track offset voltage for shifting the position of the focus lens in the horizontal direction is applied to an actuator (not shown) for moving the focus lens. The optical axis shift compensation operation is performed to move the beam spot formed in the area D to the center position (S84), so that the signal recorded on the optical disc is read and reproduced normally.

As described above with reference to FIGS. 4 and 6, in addition to the focus error signal or the optical axis error signal, the level of the electric signal for each region photoelectrically converted from the light receiving element divided into a plurality of areas is compared with each other. Determine the position of the beam spot formed in the laser beam, and apply a track offset value corresponding to the result of the determination to the actuator to perform an optical axis distortion compensation operation so that the beam spot is moved to the center position of the light receiving element and recorded on the optical disk. The read signal can also be read and played back normally.

In addition, as described above with reference to FIG. 7, the optical axis is primarily detected based on the focus error signal, and when the optical axis is distorted, as described above, the area-specific electric signal outputted by photoelectric conversion from the light receiving element is output. Comparing the levels with each other, the position of the beam spot formed in the light receiving element is determined, and a track offset value corresponding to the result of the determination is applied to the actuator so that the beam axis is shifted to the center position of the light receiving element. By performing the operation, a signal recorded on the optical disc can be read and reproduced normally.

As mentioned above, preferred embodiments of the present invention are disclosed for the purpose of illustration, and those skilled in the art can improve and change various other embodiments within the spirit and technical scope of the present invention disclosed in the appended claims below. , Replacement or addition would be possible.

In the optical pickup distortion compensation method according to the present invention as described above, the beam spot emitted from the light emitting element such as a laser diode and reflected by the recording surface of the optical disk, the center of the light receiving element such as a photodiode When formed at a position off the XY axis from the position, the process of mounting the optical pickup in an optical disk device such as a disk driver by variably adjusting the position of the focus lens in the horizontal direction so that the beam spot is formed at the center position of the light receiving element. It is a very useful invention to be able to compensate for the optical axis distortion caused by the physical torsion, etc., in the normal regeneration operation, and to automatically compensate the optical axis distortion without a separate adjustment process.

Claims (12)

Detecting a focus error signal according to movement of the optical pickup when the optical disc is mounted; Determining whether a position of a beam spot formed in the light receiving element is formed at a center position based on the waveform or level of the detected focus error signal; And And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination. . The method of claim 1, In the second step, the waveform of the detected focus error signal is detected as a waveform which is asymmetrical with each other in the high section and the low section, and the level of the focus error signal in the high section is lower than a predetermined reference high level. Is detected, it is determined that the beam spot is formed in the B or D area of the light receiving element divided into four areas A, B, C and D on the basis of the clockwise direction. Optical axis distortion compensation method. The method of claim 1, In the second step, the waveform of the detected focus error signal is detected as a waveform that is asymmetric with each other in the high section and the low section, and the absolute magnitude of the focus error signal in the low section is determined by the focus error signal in the high section. In the case of larger than the absolute size, it is determined that the beam spot is formed in the B or D region of the light receiving element divided into four areas A, B, C and D on the basis of the clockwise direction. Optical axis distortion compensation method. The method of claim 1, The third step may include: compensating by applying a track offset voltage of an actuator for variably moving the focus lens in any one horizontal direction when it is out of the center position as a result of the determination; Determining whether to compensate after the compensation; And recompensating in a direction opposite to the direction when the compensation is not completed as a result of the determination. Detecting an optical axis error signal according to the optical pickup movement when the optical disc is mounted; Determining whether the position of the beam spot formed in the light receiving element is formed at the center position based on the waveform or level of the detected optical axis error signal; And And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination. . The method of claim 5, The optical axis error signal includes a difference signal between the left divided region of the light receiving element, the electrical signals output from the right divided region, or an upper divided region of the light receiving element, 2. A compensation method for optical axis distortion in an optical pickup, characterized in that it is a difference signal between electrical signals respectively output from the divided regions. The method of claim 6, In the second step, a difference signal is smaller than zero between the left divided region and the right divided region of the light receiving element, and the upper division of the light receiving element is performed. If the difference signal is greater than zero between the area and the electrical signals respectively output from the lower divided area, the area B of the light receiving element divided into four areas A, B, C and D on the clockwise basis. And optical beam distortion correction method for optical pickup, characterized in that it is determined that a beam spot is formed. The method of claim 6, In the second step, the difference signal is greater than zero between the left divided region of the light receiving element and the electric signals output from the right divided region, and the upper portion of the light receiving element is divided. If the difference signal between the area and the electrical signals respectively output from the lower divided area is less than zero, it is applied to the D area of the light receiving element divided into four areas A, B, C and D on the basis of the clockwise direction. And optical beam distortion correction method for optical pickup, characterized in that it is determined that a beam spot is formed. Detecting a respective electric signal that is photoelectrically converted by the light receiving element divided into a plurality of areas in the optical pickup when the optical disk is mounted; Comparing the electric signals for each detected region, and determining whether a position of a beam spot formed in the light receiving element is formed at a center position; And And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination. . The method according to claim 5 or 9, And the step (3) is to apply a track offset voltage of an actuator for variably moving the focus lens in a horizontal direction when it is out of the center position as a result of the determination. A step of detecting a focus error signal and an optical axis error signal while moving the focus lens in the direction of the optical disc at a predetermined initial lower position when mounting the optical disc; If the waveform and signal level of the focus error signal are abnormally detected, determining whether the position of the beam spot formed in the light receiving element is out of the center position based on the optical axis error signal; And And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination. . When the optical disc is mounted, the focus lens is moved upward in the direction of the optical disc at a predetermined initial lower position, and each electric signal photoelectrically converted by the light receiving element divided into a plurality of areas within the optical pickup is moved. Detecting 1 step; If the waveform and signal level of the focus error signal are abnormally detected, determining whether the position of the beam spot formed in the light receiving element is out of the center position based on the electric signal for each region; And And determining the beam spot at the center position by variably moving the focus lens in the horizontal direction when it is out of the center position as a result of the determination. .