KR20040043555A - Device and the method for tilt detection - Google Patents

Abstract

PURPOSE: A device and a method for detecting tilt are provided to compensate the tilt generated when a high density disc is recorded/played, and compensate crosstalk and secure a recording/playback margin of the optical aberration by offering a tilt detector to control the disc tilt corresponding to the distortion of an optical shaft. CONSTITUTION: A beam splitter(301) reflects/passes an incident beam from a light source. An objective lens(302) collects the beam reflected from the beam splitter on the disc(306). A reflecting mirror(303) reflects the beam passing the beam splitter by installing to the back of the beam splitter. A collimating lens(304) collimates the reflected beam if the beam reflected from the reflecting mirror is reflected again by the beam splitter. A tilt diode(305) detects the tilt by the beam collimated from the collimator lens and the beam passing the beam splitter again while reflecting from the disc after passing the objective lens.

Description

Tilt detection device and its detection method {DEVICE AND THE METHOD FOR TILT DETECTION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt detection device and a detection method thereof, and more particularly to a tilt detection device and a detection method thereof capable of compensating for a tilt occurring in recording and reproducing a high density disc.

In general, optical discs have been commercialized by commercially available compact discs (CDs) and commercially available DVDs (Digital Versatile Discs) with improved recording capacity. As the optical disc becomes denser, the focusing recording mark and track pitch become smaller. In addition, the higher the density of the disk, the shorter the distance from the surface of the optical disk to the information recording surface.

An ideal optical disc has an angular deviation of the optical disc surface, that is, its bending angle is '0', but the eccentricity of the optical disc itself generated during the manufacture of the optical disc, the mechanical mechanism of the turntable or spindle motor of the spindle motor, and the surface supporting the optical pickup. Because tolerances exist realistically, some degree of tolerance is acknowledged. For example, in the case of DVD-RAM, angular division permits ± 0.7 ° in the radial direction (R) of the optical disc and ± 0.3 ° in the tangential direction (T).

However, even if the optical disk within this tolerance, the rotational speed of the optical disk is increased, the vibration amount is increased, the tilt is changed in the radial direction (R) and the amount is generated more.

Therefore, in order to improve the reliability of the optical disc, it is necessary to store and reproduce high quality signals on the optical disc. If there is a tilt angle of the recording surface of the optical disk with respect to the optical axis of the optical beam, aberrations occur at the light spot, which prevents recording and reproduction of high quality signals on the optical disk. Make it difficult Therefore, in order to record and reproduce signals on the optical disc, it is necessary to accurately detect the above-described tilt angle and correct this tilt angle.

Further, in the optical disc apparatus for reproducing and recording the corresponding high density optical disc, the optical axis of the light beam focused on the optical disc must be perpendicular to the optical disc surface in order to accurately record and reproduce data on the recording surface of the disc.

So, in order to realize this, a method of shortening the laser wavelength and increasing the numerical aperture NA of the objective lens has been adopted. It occurs proportionally (mainly coma aberration), and thus the tilt margin also decreases in proportion to (λ / (NA) ^ 3), making it impossible to record or reproduce data signals in an optimal state.

FIG. 1 is a diagram illustrating a tilt generation region while schematically illustrating a configuration of an optical pickup apparatus using a tilt sensor according to the related art, and FIG. 2 is a diagram illustrating a path of a beam in the optical pickup apparatus according to the related art. As shown in Fig. 1, first, an optical head 101 for emitting a light source and recording and reproducing a beam on a disk, a spindle motor 102 for seating the disk 105, and the optical head 101 And a tilt sensor (103) for detecting the tilt generated in the spindle motor (102) and a tilt mechanism (104) for compensating the tilt detected by the tilt sensor (103). It is composed.

The optical head 101 is a collimator (not shown) for making the emitted beam into a parallel beam, a reflection mirror 201 for total reflection of the beam passing through the collimator, and a beam totally reflected by the reflection mirror 201. And an objective lens 202 for condensing the light on the disk 105.

As shown in FIG. 2, the emitted light is incident on the objective lens 202 through a reflection mirror and the incident beam is focused by the objective lens 202 to focus on the disk 105.

The focus on the disk is then diffracted and reflected by the pits or marks formed on the disk, which in turn are directed to the light-receiving portion through the objective lens and the reflection mirror, and become the focus, tracking control signal and reproduction data.

On the other hand, in the tilt generation region shown in FIG. 1, the tilt generated from the disk is the optical axis skew (t1) remaining after assembly in the optical head, and the spindle tilt (t2) generated while seating and rotating the disk on the spindle motor. ), There is a disc tilt t3 that occurs while producing a disc.

Therefore, the tilt sensor provided on the optical head for compensating the generated tilt includes a light emitting part for irradiating infrared rays in a direction perpendicular to the optical disk surface, and a light receiving part for receiving a beam reflected from the optical disk. It is configured to include.

This is because the tilt sensor is placed on the optical axis of the optical head to move the optical head in and out with respect to the disk when the disk is retracted to obtain tilt information or to obtain tilt information during recording and playback. The correction is performed by using a to enable the reproduction of a high density disk.

However, the tilt detection method using the tilt sensor 103 has a large irregularity due to the difference in assembling attitude when assembling the tilt sensor, and the position of the tilt sensor and the position of the light beam irradiated to the optical disk cannot be installed at the same position. As a result, it is impossible in principle to accurately detect and compensate for disc tilt.

In particular, a higher density disk causes a serious problem in that tilt correction cannot be performed when the direction of deflection of the disk is reversed at the position of the tilt sensor and the position of the light beam.

In addition, the tilt detection method using the tilt sensor as described above not only contributes to an increase in the cost of the optical disk device, but also constrains the space inside the thinned optical disk device.

In the prior art, only tilt in one direction (radial) on the axis can be compensated, which can only be detected and compensated for the mixed spindle tilt amount and the disk tilt amount in one axis direction. Compensation for remaining optical axis misalignment in the biaxial direction cannot be compensated.

In addition, a higher density disc requires more accurate tilt detection means to correct crosstalk (interference between signals) that occurs during recording and playback between adjacent tracks.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tilt detection device and a method for detecting the same, capable of compensating for tilts generated in recording and reproducing a high density disk.

In addition, the present invention provides a tilt detection means capable of adjusting the disc tilt in accordance with the optical axis distortion remaining in the optical head, in particular, to secure crosstalk correction occurring in high-density recording reproduction and to secure recording reproduction margin of optical aberration. There is this.

1 is a view showing a tilt generation area while schematically showing the configuration of an optical pickup device using a tilt sensor according to the prior art.

2 is a view showing the path of the beam in the conventional optical pickup device.

3 is a view schematically showing the configuration of a tilt detection device according to the present invention.

4 illustrates that a reference beam is defined by adjusting a reflecting mirror in accordance with the present invention.

5 is a diagram illustrating a tilt detection method of a tilt diode according to the present invention.

<Description of the symbols for the main parts of the drawings>

301 --- Beam Splitter 302 --- Objective Lens

303 --- Reflective Mirror 304 --- Condensing Lens

305 --- Tilt Diode 306 --- Optical Disc

In order to achieve the above object, the tilt detection device according to the present invention,

A beam splitter for reflecting and transmitting the beam incident from the light source;

An objective lens for condensing on the disk with respect to the beam reflected by the beam splitter;

A reflection mirror provided at a rear end of the beam splitter and reflecting the beam transmitted by the beam splitter;

A condenser lens for condensing the reflected beam when the beam reflected by the reflection mirror is reflected back by the beam splitter;

And a tilt diode that passes through the objective lens and is reflected on the disk and detects the tilt by the beam transmitted through the beam splitter and the beam focused by the condenser lens.

In particular, the characteristic is that the reference beam is defined by adjusting the reflection mirror with respect to the beam reflected by the reflection mirror.

In particular, the beam splitter is characterized in that a predetermined ratio is reflected and a predetermined ratio is transmitted to the incident beam.

In particular, the beam splitter is characterized in that it is configured to be 95% reflected and 5% transmitted to the incident beam.

In addition, the tilt detection method according to the present invention in order to achieve the above object,

Adjusting a reflection mirror with respect to the beam emitted from the reference light source, and compensating for tilt to define a reference beam;

Defining an optical axis using a master disk for the beam emitted from the reference light source;

Detecting a tilt beam in which the reproduction beam emitted from the reproduction light source is reflected on the disc through the objective lens and transmitted through the beam splitter;

Detecting the tilt by comparing the tilt beam with reference to the reference beam defined in the step of defining the reference beam;

And a step of correcting the tilt by driving the tilt mechanism with respect to the detected tilt.

Here, in particular, the step of defining the reference beam is characterized in that the reflection mirror is adjusted in the radial direction and the tangential direction to compensate for the tilt.

Here, the characteristic is that the tilt is corrected by driving the radial adjustment mechanism and the tangential adjustment mechanism in the step of driving the tilt mechanism with respect to the detected tilt.

According to the present invention as described above, the tilt caused in recording and reproducing the high density disk can be compensated.

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

3 is a view schematically showing the configuration of the tilt detection apparatus according to the present invention. As shown therein, a beam splitter 301 for reflecting and transmitting the beam incident from the light source; An objective lens (302) for condensing on the disc with respect to the beam reflected by the beam splitter (301); A reflection mirror (303) provided at a rear end of the beam splitter (301) and reflecting the beam transmitted by the beam splitter (301); A condenser lens 304 for condensing the reflected beam when the beam reflected by the reflection mirror 303 is reflected back by the beam splitter 301 again; Tilt diode 305 that passes through the objective lens 302 and is reflected on the disk 306 to detect tilt by a beam transmitted through the beam splitter 301 and a beam focused by the condenser lens 304. It is configured to include).

The tilt detection method according to the present invention will be described with reference to FIG. 3 configured as described above.

First, a step of adjusting the reflection mirror 303 with respect to the beam emitted from the reference light source and compensating the tilt to define the reference beam is performed.

More specifically, first, the beam emitted to the reference light source is incident to the beam splitter 301. At this time, the beam splitter 301 transmits a predetermined amount to the total amount of light incident on the light source, and the predetermined amount is reflected on the coated reflective surface (for example, 5 to 10% transmission). , 90-95% reflex).

4 is a diagram illustrating that a reference beam is defined by adjusting a reflection mirror according to the present invention. As shown therein, 5% of the beams passing through the beam splitter 301 go to a reflection mirror installed at the rear end of the beam splitter 301. The beam reflected by the reflective mirror 303 is reflected by 95% of the beam splitter 301 again and is formed on the tilting photodiode 305 through the condenser lens 304.

About 5% of the reference light source is received by a quadrant photodiode for tilt detection, and circuitally defines a reference beam such that the difference signal of (A + B)-(C + D) becomes zero, and tilts the reflection mirror. After adjusting, fix it. In this case, the reflection mirror is adjusted in radial and tangential directions with respect to the reference light source to compensate for the amount of tilt remaining in the optical head.

Next, a step of defining an optical axis using a master disc for beams emitted from the reference light source is performed.

In more detail, if the posture of the objective lens is also compensated and assembled on the same axis with respect to the remaining amount of tilt in the optical head based on the master disk having no tilt, the tilt generated from the optical head is kept on the same axis. do.

When the disc is compensated for by detecting the tilt of the spindle (t2) that occurs while seating and rotating the disk on the spindle motor and the disk tilt (t3) that occurs while manufacturing the disk, the disk recording surface and the optical axis of the optical aberration are the smallest. Recording and playback in the vertical state can be achieved.

Subsequently, a step of detecting the tilt beam in which the reproduction beam emitted from the reproduction light source is reflected on the disc through the objective lens 302 and has passed through the beam splitter 301 is performed.

In more detail, 95% of the total beams reflected by the beam splitter 301 pass through the objective lens 302 which focuses the beam to form a beam spot on the disk. The beam diffracted and reflected by the pit or mark formed on the disk 306 goes back to the beam splitter 301 and goes to the light receiving system which reflects 95% to become the focus, tracking control signal and reproduction data.

In addition, a 5% tilt beam having tilt information of the disk transmitted from the beam splitter 301 is formed on the quadrant tilt diode via the condenser lens 304.

Then, the tilt beam is detected by comparing the tilt beam with reference to the reference beam defined in the step of defining the reference beam.

5 is a diagram illustrating a tilt detection method of a tilt diode according to the present invention. As shown here, the difference between the radial tilt (A + B)-(C + D) or the tangential tilt (A + D)-(B + C), depending on the signal detected on the quadrant tilt diode. Will be adjusted by the difference signal.

On the other hand, the radial tilt (R tilt) is based on the inclination angle of the recording surface of the optical disk with respect to the optical axis of the optical beam and the disk R tilt caused by the disk torsion or surface imbalance due to the rotation of the disk. It consists of a drive R tilt due to the inclination angle of the installation or tilt platform. In essence, the disc R tilt and the drive R tilt are not distinguished and are commonly referred to as R tilt.

The tangential tilt (T tilt) is an inaccurate optical head based on the tilt angle of the recording surface of the optical disk with respect to the optical axis of the optical disk and the disk T tilt caused by a wave of disk rotation, surface precision error in the disk, and the like. It consists of a drive T tilt due to the inclination angle of the installation or tilt platform. In essence, the disc T tilt and the drive T tilt are not distinguished and are commonly referred to as T tilt.

Subsequently, driving the tilt mechanism with respect to the detected tilt is performed to correct the tilt.

According to the detected tilt, a tilt control signal is generated in the radial direction by the difference signal of (A + B)-(C + D) circuit to drive the tilt mechanism, and (A + D)-(B + C) By making the tilt control signal in the tangential direction as much as the difference signal of D, the tilt mechanism is driven so that the disc recording surface and the optical axis are always perpendicular to each other so that the higher density discs can compensate for the crosstalk required and the optical disc of the recording system. It is possible to secure the recording and reproducing margin of the optical aberration in the apparatus.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the tilt detection device and the detection method thereof according to the present invention can tilt the light generated when recording and reproducing a high density disk.

In addition, the tilt detection apparatus and the detection method according to the present invention are not only tilted when the disk is recorded and played back, and tilted when the disk is seated and played on the spindle, as well as the remaining optical axis distortion after assembly of the optical head. By providing the tilt detection means capable of adjusting the disc tilt correspondingly, it is possible to secure the crosstalk correction occurring in the high density recording and reproduction and the recording and reproduction margin of the optical aberration.

Claims (7)

A beam splitter for reflecting and transmitting the beam incident from the light source; An objective lens for condensing on the disk with respect to the beam reflected by the beam splitter; A reflection mirror provided at a rear end of the beam splitter and reflecting the beam transmitted by the beam splitter; A condenser lens for condensing the reflected beam when the beam reflected by the reflection mirror is reflected back by the beam splitter; And a tilt diode which passes through the objective lens and is reflected on the disk and detects the tilt by the beam transmitted through the beam splitter and the beam focused by the condenser lens. The method of claim 1, And tilting the reflection mirror with respect to the beam reflected by the reflection mirror to define a reference beam. The method of claim 1, And the beam splitter is configured to reflect a predetermined ratio with respect to an incident beam and transmit a predetermined ratio. The method of claim 1, The beam splitter is configured to be 95% reflected and 5% transmitted to the incident beam. Adjusting a reflection mirror with respect to the beam emitted from the reference light source, and compensating for tilt to define a reference beam; Defining an optical axis using a master disk for the beam emitted from the reference light source; Detecting a tilt beam in which the reproduction beam emitted from the reproduction light source is reflected on the disc through the objective lens and transmitted through the beam splitter; Detecting the tilt by comparing the tilt beam with reference to the reference beam defined in the step of defining the reference beam; And tilting the tilt mechanism by driving the tilt mechanism with respect to the detected tilt. The method of claim 5, And defining the reference beam to compensate for the tilt by adjusting the reflection mirror in a radial direction and a tangential direction. The method of claim 5, And tilting the radial adjustment mechanism and the tangential adjustment mechanism to correct the tilt in the step of driving the tilt mechanism with respect to the detected tilt.