KR20080013275A - Apparatus and method for reproducing meduim - Google Patents

Abstract

A reproducing apparatus and a reproducing method are provided to compensate for an error of gap distance and to improve RF signal quality by using an RF signal level detected through photoelectric units. A reproducing apparatus comprises an SIL(122,solid immersion lens) and an objective lens(121), actuators(120), photoelectric units(113,115), and a control part(200). The beam emitted from a light source is projected to a recording medium(123). The photoelectric units detect an RF signal from the beam reflected from the recording medium. The control part compensates for an error of the gap distance by using the RF signal level detected through the photoelectric units. A gap servo operation is executed at the gap distance where the average value of the RF signal level is the maximum.

Description

Playback device and method for playback {Apparatus and method for reproducing meduim}

1 is a side view of a SIL and a recording medium provided in the near field data recording apparatus.

FIG. 2 A light spot observing light totally reflected from the reflecting surface of SIL.

3 is a diagram showing a relationship between a feedback light amount and a gap;

4 illustrates a playback apparatus according to an embodiment of the present invention.

5 illustrates an RF signal observed through a photo detector.

6 is a flowchart for explaining a playback method according to the embodiment of the present invention;

The present invention relates to a reproducing apparatus, and a reproducing apparatus and a reproducing method capable of compensating a distance (ie, a gap) between a recording medium and a lens to further improve the RF signal quality during a gap servo operation for reproducing data. It is about.

In order to meet the demand for miniaturization of the size of the recording medium, a narrow track width can have a high density recording capacity. However, the limitation due to the difference in the layer structure of the recording medium including the protective layer, the recording layer, and the reflective layer and consequently the condensing method, the diffraction of the spot size of the light collected on the recording medium to form bits in the recording layer of the recording medium Due to limitations such as limitations, studies on optical recording and reproducing methods for overcoming such limitations are being actively conducted.

In order to solve the problem of the conventional far-field optical recording and reproducing method, as a method for increasing the recording density in a region where no light diffraction occurs recently, an optical recording and reproducing method using a near-field Is being proposed.

1 is a side view of a SIL and a recording medium provided in a near field data recording apparatus, and is a light spot in which light is totally reflected from the reflecting surface of FIG. 2 SIL, and FIG. 3 is a view showing a relationship between a feedback amount and a gap. .

A SIL (Solid Immersion Lens) 2 having a total reflection surface is provided between the recording medium 1 and the objective lenses OL and 3 so as to totally reflect light above a predetermined critical angle, and between the SIL 2 and the recording medium. Has a gap d.

The light passing through the objective lens 3 is incident on the SIL 2 before being incident on the recording medium 1, and is incident on the SIL 2 at a predetermined threshold angle θ or more. Is totally reflected at the reflection surface of the SIL 2 and moved to the photo detector for observing it.

Then, in relation to the size of the light formed on the reflecting surface of the SIL 2 and the distance d between the SIL 2 and the recording medium 1, the wavelength? Of the light incident on the SIL 2 is d. The area defined by ≤ λ / 2 is a near-field.

The state where the interval d satisfies d? Lambda / 2 and light does not penetrate into the data recording / reproducing layer is called a far-field state.

By the way, in the far field state, all the light incident on the SIL 2 cross section at an angle equal to or greater than the critical angle θ is totally reflected to become the feedback light. Therefore, as shown in Fig. 3, the total reflection feedback light in the far field state is a constant value.

On the other hand, in the near field state, part of the light incident on the reflective surface of the SIL 2 at an angle greater than or equal to the critical angle θ is the recording medium on the reflective surface of the SIL 2 (ie, the reflective boundary surface) as described above. It permeates the data recording / reproducing layer of (1).

Therefore, as shown in FIG. 3, it can be seen that the return light amount of the totally reflected light decreases exponentially as it approaches the data recording / reproducing layer (exactly, the surface of the recording medium) of the recording medium 1.

Therefore, when the cross-sectional position of the SIL 2 is in the near field state, if feedback servo is performed as a gap error signal on the linear portion whose total reflection feedback amount changes according to the size of the interval d, the cross-section of the SIL 2 and The gap with the data recording / reproducing layer surface of the recording medium 1 can be controlled constantly.

For example, as shown in Fig. 3, when the control is performed such that the total reflection feedback light amount becomes the control target value P, the interval d is kept constant.

Of the light incident on the SIL 2, light incident at a critical angle θ or higher is observed in a relatively bright area 5 as shown in FIG. 2, and light incident at or below the critical angle θ is recorded. Infiltrated into the medium, it is observed in the dark area 6 as shown.

Conventionally, when reproducing data, a gap servo operation is performed to keep the interval between the recording medium 1 and the SIL 2 constant so that RF signal deviation does not occur in the near field state. There is a problem that an RF signal deviation occurs depending on various assembly conditions or the state of the recording medium.

Therefore, since the servo operation is performed with a constant gap distance between the recording medium and the lens (or SIL), there is a problem in that data recorded on the recording medium is not reproduced correctly.

The present invention is proposed to solve the above problems, and an object of the present invention is to propose a reproducing apparatus and a reproducing method capable of compensating a gap distance required for a gap servo operation so that the RF signal quality can be improved.

A reproducing apparatus according to an embodiment of the present invention comprises: an SIL and an objective lens for causing a beam emitted from a light source to be incident on a recording medium; An actuator for gap servo operation of the recording medium; Photoelectric means for detecting an RF signal from a beam reflected from the recording medium; And a controller for correcting the gap distance using the RF signal level detected through the photoelectric means.

According to another aspect of the present invention, there is provided a reproducing method, comprising: rotating a loaded recording medium; Operating an actuator for a gap servo operation of the recording medium while varying a gap distance for a predetermined time; Detecting an RF signal level from a beam reflected from the recording medium; And setting a gap distance for a gap servo operation using the magnitude of the RF signal level.

Hereinafter, an optical recording and reproducing apparatus according to the present invention will be described in detail with reference to the accompanying drawings. However, one of ordinary skill in the art who understands the spirit of the present invention may easily propose another embodiment by adding, adding, deleting, or modifying elements within the scope of the same spirit, but this also belongs to the scope of the present invention. I will say.

4 is a diagram illustrating a playback apparatus according to an embodiment of the present invention.

Referring to FIG. 4, a reproducing apparatus according to the present invention provides an RF signal for recording or reproducing data on a recording medium 123, and a gap servo signal for controlling an interval between the recording medium 123 and the SIL 122. An actuator 120 having an optical block for detection, a SIL 122 and an objective lens 121 having light incident on the recording medium 123 and incident light reflected from the recording medium 123 being incident; A control unit 200 for controlling the gap servo operation of the actuator 120 is included.

The optical block includes a laser diode 110 that emits predetermined light (eg, blue light of 405 nm band), a collimator lens 111 that converts the beam emitted from the laser diode 110 into parallel light, and The first polarized beam splitter (PBS) 112 and the second polarized beam splitter 114 for transmitting or reflecting the incident beam according to the polarization component of the beam, and controlling the divergence angle or convergence angle of the beam to adjust the size of the light And an expander 116, and a QWP (Quarter Wave Plate) 117 for converting the wavelength of the incident beam.

The optical block includes a second photo detector (second photoelectric means 115) for detecting an RF signal reflected from the recording medium 123 and incident through the second optical beam splitter 114. A first photodetector (first photoelectric means) 113 is included for detecting a gap error signal reflected from the recording medium 123 and incident through the first polarization beam splitter 112.

For reference, it should be noted that the present invention is explained by exemplifying a photo detector as a photoelectric means.

The actuator 120 includes a SIL 122 for focusing the incident beam on the recording medium 123, and an objective lens 121 having a predetermined refractive index.

The controller 200 corrects a gap distance by using an RF signal level detected through the second photo detector 115 during a gap servo operation driven by the actuator 120.

In detail, when the recording medium 123 is rotated, the actuator 120 performs a gap servo operation for maintaining a distance between the recording medium 123 and the SIL 122 at a predetermined distance. The reproducing apparatus is operated in a mode for correcting the gap distance for a predetermined time.

That is, the controller 200 controls the reproduction apparatus to operate in a mode for re-adjusting the servo gap (gap) between the SIL 122 and the recording medium 123 for a predetermined time, and in this mode, the actuator 120 Is moved up and down a predetermined distance with respect to the recording medium.

In addition, the controller 200 detects the RF signal that appears while the actuator 120 moves in the vertical direction through the second photo detector 115.

The distance between the recording medium 123 and the SIL 122 is changed by the movement of the actuator 120, thereby changing the level of the RF signal observed through the second photo detector 115.

In the mode for correcting the gap distance, the controller 200 may store the level of the RF signal observed through the second photo detector 115 and the gap distance in the corresponding RF signal.

In this case, the RF signal observed through the second photo detector 115 may appear as shown in FIG. 5.

FIG. 5 illustrates an RF signal observed through the photo detector. When the gap between the recording medium 123 and the SIL 122 is kept constant, the magnitude of the RF signal level will be kept constant.

However, when the gap distance caused by the movement of the actuator 120 is changed, the size of the RF signal level will also be changed, and as the size of the RF signal level is larger, the data to be played back will be reproduced more accurately. Setting the gap distance in consideration of the magnitude of the signal level is performed.

For example, while varying the gap distance by moving the actuator 120 up and down for a predetermined time, the gap servo is used for the gap distance when the magnitude of the RF signal level observed through the second photo detector 115 is maximized. It can be set as the gap distance for

In addition, the gap distance at which the RF signal level observed through the second photo detector 115 is greater than or equal to a predetermined reference value may be set as a gap for the gap servo.

In the mode for correcting the gap distance, the gap distance caused by the movement of the actuator 120 is varied, and the process of calculating the gap distance that is most suitable for data reproduction is performed by confirming the RF signal level observed therefrom. Is performed.

In the mode for correcting the gap distance, the RF signal is detected from the rotated recording medium 123 through the second photo detector 115 and the user cannot display the reproduced data.

In addition, after the gap distance using the RF signal level is set, the data reproduced while the servo operation by the actuator 120 is performed is displayed to the user.

The operation of the optical recording and reproducing apparatus configured as described above is as follows.

The light emitted from the laser diode 110 is converted into parallel light in the collimator lens 111, and then, in the expander 116 via the first polarizing beam splitter 112 and the second polarizing beam splitter 114. The divergence angle or convergence angle is controlled.

In addition, the light is linearly polarized by the QWP 117 into circularly polarized light and is incident to the reflection mirror 119.

The light reflected by the reflection mirror 119 is incident on the recording medium 123 after passing through the objective lens 121 and the SIL 122. However, at this time, light incident on the reflective surface of the SIL 122 at a predetermined critical angle or more is totally reflected at the reflective surface of the SIL 122 and re-incident to the reflective mirror 119.

In addition, a coil and a magnetic circuit are formed in the actuator 120 to perform servo operation for gap error and tracking error.

Meanwhile, the light reflected from the recording medium 123 is converted into linearly polarized light in the QWP 117. However, it is changed to the polarization direction perpendicular to the original polarization direction.

In the near field optical recording and reproducing apparatus, the SIL is caused by a coupling between the SIL 122 and the recording medium 123 and the refractive index between the SIL 122 and the recording medium 123 and the air. Of the light incident on 122, light incident at a critical angle or more is totally reflected, and the rest is incident on the recording medium 123.

Accordingly, light having a polarization component that can be reflected by the second polarization beam splitter 114 among the light reflected by the recording medium 123 is incident to the second photo detector 115, and the second photo is incident on the second photo detector 115. The signal incident on the detector 115 becomes an RF signal.

The second photo detector 115 converts the RF signal into an electrical signal to reproduce data stored in the recording medium 123. However, as described above, the RF signal that can be observed through the second photo detector 115 may not be displayed to the user in the operation mode for gap distance correction by the controller 200.

In addition, the light totally reflected by the SIL 122 is reflected through the first polarization beam splitter 112 and is incident to the first photo detector 113, and the signal incident to the first photo detector 113 is It is a signal for detecting the tilt amount of the recording medium 123.

6 is a flowchart illustrating a playback method according to an embodiment of the present invention.

First, in order to reproduce the data recorded on the recording medium 123, the inserted recording medium 123 is rotated for the servo operation (S101).

Then, a gap servo operation is performed to keep the gap between the recording medium 123 and the SIL 122 constant (S103).

In addition, an operation (S200) for correcting a gap distance between the recording medium 123 and the SIL 122 is performed. Although this operation is described as being performed after the previous step S103, the recording medium 123 is inserted. Of course, it can be operated in a mode for correcting the gap distance.

In the mode for correcting the gap distance, the actuator 120 having the SIL 122 and the objective lens 121 is moved up and down with respect to the recording medium 123 for a predetermined time, thereby causing the recording medium ( The gap distance between 123 and SIL 122 is varied (S201).

In addition, while the actuator 120 moves up and down a predetermined distance for a predetermined time, the controller 200 checks an RF signal level observed through the second photo detector 115 (S203).

The controller 200 resets the gap distance for the servo operation by using the RF signal level observed through the second photo detector 115.

For example, the size of the RF signal level that varies according to the vertical movement of the actuator 120 may be stored and the average values of the RF signal levels may be compared (S205).

That is, the average value of the RF signal level according to the varying gap distance may be dataged, and the gap distance when the average value of the RF signal level is largest may be stored. The gap distance at this time may be reset to the gap distance of the gap servo operation performed at the time of reproducing the recording medium (S207).

However, when the difference between the gap distance to be corrected and the previous gap distance is within a predetermined value, the above-described gap distance correction may not be performed. For example, the compensated gap distance B and the preset gap may be prevented. When the difference in the distance A does not differ by more than 50% (│BA│ <A × 0.5), the gap distance correction may not be performed.

After the mode for correcting the gap distance is finished, a gap servo operation by the actuator 120 is performed with the corrected gap distance (S105), and the data recorded on the recording medium 123 Regeneration is performed.

According to the above-described embodiment of the present invention, the gap distance required for the gap servo operation is corrected by using the RF signal actually reproduced, so that data reproduction can be made more accurately.

According to the embodiment of the present invention as proposed, there is an advantage that can compensate the gap distance required for the gap servo operation to improve the RF signal quality.

Claims (8)

An SIL and an objective lens for allowing the beam emitted from the light source to be incident on the recording medium; An actuator for gap servo operation of the recording medium; Photoelectric means for detecting an RF signal from a beam reflected from the recording medium; And And a controller for correcting the gap distance using the RF signal level detected through the photoelectric means. The method of claim 1, And a gap servo operation is performed with a gap distance when the average value of the RF signal levels detected from the photoelectric means becomes maximum. The method of claim 1, And reproducing a gap even in a gap distance in which the magnitude of the RF signal level is greater than or equal to a predetermined value. The method of claim 1, And upon detecting an RF signal level for correcting the gap distance, the actuator is driven such that a gap between the recording medium and the SIL varies for a predetermined time. The method of claim 1, And the control unit does not perform the correction of the gap distance when the difference between the gap distance B set from the RF signal level and the preset gap distance A is within a predetermined value. A recording medium is loaded and rotated; Operating an actuator for a gap servo operation of the recording medium while varying a gap distance for a predetermined time; Detecting an RF signal level from a beam reflected from the recording medium; And And setting a gap distance for a gap servo operation by using the magnitude of the RF signal level. The method of claim 6, And a gap servo operation by driving the actuator according to the set gap distance. The method of claim 6, The gap distance setting is a gap distance when the average value of the RF signal levels detected for a predetermined time becomes maximum.

Images