KR100552899B1 - High Density Optical Recording Media and Optical Pickup Apparatus For Reproducing The Media and Recording or Reproducing Apparatus Of The Media and Methods Thereof - Google Patents

Abstract

The present invention relates to a high density optical recording medium, an optical pickup apparatus for reproducing the same, a recording or reproducing apparatus for the optical recording medium, and a reproduction method.

A high density optical recording medium, an optical pickup apparatus for reproducing the same, an optical recording medium recording or reproducing apparatus, and a reproducing method have a structure in which tracks on which information is recorded are alternated with at least two different track pitches, An optical recording medium having recorded thereon information for identifying another track pitch; An optical pickup apparatus for providing an asymmetric super-resolution light beam relative to the track crossing direction; A reproduction method for detecting a reproduction signal by controlling the light beam such that a side lobe of the asymmetric super-resolution light beam is placed at a wide track pitch, and condensing the light beam from the light source onto the recording medium and reflecting the light; An optical pickup for receiving a beam; And a signal processing unit for signal-processing and outputting the signal detected and converted by the optical pickup, and a control unit for controlling the optical pickup in accordance with a signal output from the signal processing unit. And an information recording and reproducing apparatus for detecting the information for identifying the different track pitch and for controlling the optical pickup according to the detected information.

The optical recording medium of the present invention has a high density recording capacity and is suitable for crosstalk reduction, and the optical pickup apparatus and the reproduction method of the optical recording medium can effectively reduce crosstalk and obtain accurate reproduction signals.

Description

High Density Optical Recording Media and Optical Pickup Apparatus For Reproducing The Media and Recording or Reproducing Apparatus Of The Media and Methods Thereof}

The present invention relates to a high density optical recording medium, an optical pickup apparatus for reproducing the same, a recording or reproducing apparatus for the optical recording medium, and a reproduction method.

Optical recording media have been developed and widely distributed following commercially available CDs, and their use is further increased for recording and reproducing audio and video data and computer data. Optical recording media have been actively researched for higher density, such as narrowing the pit size and track pitch. A reproducing apparatus for reproducing a high density optical recording medium should provide a smaller light spot corresponding to the high density structure. The size of this light spot cannot be smaller than the value (diffraction limit value) proportional to [lambda] / NA depending on the wavelength [lambda] of the light source and the numerical aperture NA of the objective lens. Accordingly, in order to shorten the oscillation wavelength λ generated from the light source, the reproduction apparatus of the optical recording medium employs a short wavelength light source such as a blue laser, and attempts to realize a small size optical spot by increasing the numerical aperture NA of the objective lens. have. However, the short wavelength of the light source and the high numerical aperture of the objective lens have limitations. Recently, research on super resolution technology has been conducted as a technique for minimizing light spots. An optical pickup apparatus that applies such a super resolution technology to an optical pickup apparatus and enables high-density recording / reproducing above a threshold value has been proposed. For example, Japanese Patent Application Laid-Open No. 2-195536 and Japanese Patent Application Laid-Open 8-147748 and U.S. Patent No. 5600620)

1 is a diagram illustrating an optical pickup apparatus to which a conventional super resolution technology is applied.

In the configuration of FIG. 1, the conventional optical pickup apparatus includes a light source 2 for generating a light beam, an objective lens 12 for focusing the light beam generated from the light source 2 on the recording surface of the optical disc 1, and an optical disc ( A reproduction signal detection system 14 for converting the light beam reflected from 1) into an electrical signal, a beam splitter 10 disposed between the light source 2, the objective lens 12, and the reproduction signal detection system 14; The orthopedic prism 6 disposed between the light source 2 and the beam splitter 10, the light intensity modulator 8 disposed between the orthopedic prism 6 and the beam splitter 10, and the light source 2 and the light source 2. A collimating lens 4 is disposed between the orthopedic prisms 6.

The light beam generated from the light source 2 is converted into a parallel beam by the collimating lens 4 and is incident on the shaping prism 6.

The orthopedic prism 6 serves to shape the elliptical light beam incident from the collimating lens 4 into a circular light beam and transmit it toward the light intensity modulator 8.

As shown in FIG. 2A, the light intensity modulator 8 passes through the central portion of the light beam cross section 15 and has a shading band 7 mounted side by side in the tangential direction of the optical disc 1 to form an orthopedic prism 6. It serves to reduce the intensity of the light beam incident from the track in the transverse direction (ie, radial direction). Here, a phase plate for changing the phase of the light beam incident from the light source 2 may be used for the light intensity modulator 8 instead of the light shielding band 7.

The beam splitter 10 transmits the light beam incident from the light intensity modulator 8 toward the objective lens 12 and reflects the reflected light beam reflected from the optical disk 1 toward the reproduction signal detection system 14.

The objective lens 12 serves to focus the light beam incident from the beam splitter 10 onto the recording surface of the optical disc 1. The micro light spot 21 focused from the objective lens 12 is reduced by the light intensity modulator 8 in the light transverse direction (radial direction) so that the general light spot 20 as shown in FIG. Compared with the diameter, the diameter is reduced in the track cross direction. As the width of the main lobe 21a in the micro-light spot 21 is reduced, the track pitch Tp of the optical disc 1 can be narrowed, but as shown in FIG. 3, the side-lobe There is a problem in that the light intensity I of the () 21b becomes large. In other words, the side lobe 21b of the micro light spot 21 is irradiated to a track adjacent to the target track when the main lobe 21a irradiates the pits 1a of the target track as in FIG. The reproduction signal reproduced by the main lobe 21a in the reproduction signal detection system 14 includes noise components as the light intensity of the side lobe 21b increases, thereby increasing crosstalk.

Accordingly, it is an object of the present invention to provide a high density optical recording medium which has a high density recording capacity and is suitable for crosstalk reduction.

It is another object of the present invention to provide an optical pickup apparatus and a reproduction method using the optical pickup apparatus which can reduce crosstalk to obtain an accurate reproduction signal.

Still another object of the present invention is to record information on a high density optical recording medium and to reproduce the recorded information.

In order to achieve the above object, the high-density optical recording medium, the optical pickup apparatus for reproducing the same, the recording or reproducing apparatus for the recording medium, and the reproducing method according to the present invention alternately to at least two track pitches in which tracks on which information is recorded are different. An optical recording medium having a structure; An optical pickup apparatus for providing an asymmetric super-resolution light beam relative to the track crossing direction; A reproducing method of detecting a reproducing signal by controlling the light beam such that a side lobe of the asymmetric super-resolution light beam is placed at a wide track pitch; An optical pickup for collecting a light beam from a light source on the recording medium and receiving a reflected light beam; And a signal processor for signal processing and outputting the signal detected and changed by the optical pickup, and a controller for controlling the optical pickup according to a signal output from the signal processor. The controller detects information for identifying different track pitches and the controller is characterized in that the recording or reproducing apparatus of the recording medium controls the optical pickup according to the detected information.

Other objects and advantages of the present invention in addition to the above object will become apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 5 to 12.

5 is a diagram showing a high density optical recording medium according to the embodiment of the present invention.

Referring to FIG. 5, in the optical disc 31 of the present invention, the narrow track pitch Tpn and the wide track pitch Tpw are alternated in one rotation period. Pits 31a represented by binary information are formed at the boundary line (ie, track center line) of the narrow track pitch Tpn and the wide track pitch Tpw. The relationship between the narrow track pitch Tpn and the wide track pitch Tpw is 'Tpn <Tpw'. In contrast to the conventional optical recording medium as shown in Fig. 4, the conventional optical recording medium has the same track pitch Tp on the inner circumferential side and the outer circumferential side with respect to the track center line, but the optical recording medium of the present invention has a track center line. The track pitches of the inner circumference and the outer circumference are different from each other, and the widths of the track pitches of the inner and outer circumferences are opposite in the adjacent track centerline. In other words, from the third track center line Lr3 to the inner circumferential side, the second track center line Lr2 becomes the wide track pitch Tpw and to the outer circumferential side the fourth track pitch Lr4 becomes the narrow track pitch Tpn. From the fourth track center line Lr4 to the inner circumferential side to the third track center line Lr2 is the narrow track pitch Tpn and to the outer circumferential side to the fifth track pitch Lr5 to the wide track pitch Tpw.

Compared with the conventional method, the track pitch of the present invention has a density of (Tpn + Tpw) <2Tp, so that the track pitch is denser than that of the conventional method, so that much information can be recorded.

On the other hand, in the optical pickup apparatus described later, for side lobe control, information indicating at which position the wide track pitch Tpw is located from the track center line is recorded corresponding to the point at which the track pitch changes every revolution.

The master disk of the optical disk shown in FIG. 5 applies a photoresist film on a substrate, and then supplies a motor driving voltage V as shown in FIG. The photoresist film is fabricated by jumping by (Tpn) and wide track pitch (Tpw) and applying an exposure pulse corresponding to a pre-pit pattern of a desired shape to a laser light source.

On the track transverse direction (radial direction), the laser light source is conveyed by the narrow track pitch Tpn by the A1 voltage level and by the wide track pitch Tpw by the A2 voltage level. After manufacturing a stamper using the master disk fabricated as described above and installing the stamper on the molding machine, the substrate material is injected into the molding machine at a high temperature, and when solidified, the same prepit pattern as the prepit pattern formed on the disk is transferred. The used substrate for the disk is duplicated. Here, the stamper is produced by inverting and transferring the prepit pattern formed on the disk. In the duplicated disk substrate, a reflective layer and a protective layer for preventing deterioration of the reflective film are sequentially formed on the prepit pattern forming surface.

7 is a diagram illustrating an optical pickup apparatus according to an exemplary embodiment of the present invention.

In the configuration of FIG. 7, the light source 42 for generating the light beam, the objective lens 52 for focusing the light beam generated from the light source 42 on the recording surface of the optical disc 31, and the light beam reflected from the optical disc 31 Photodetector 60 for converting the signal into an electrical signal, a beam splitter 50 disposed between the light source 42, the objective lens 52, and the photodetector 60, the light source 42 and the beam splitter 50 Sensor disposed between the beam splitter 50 and the photodetector 60, and the phase plate 48 disposed between the shaped prism 46 and the beam splitter 50. And a collimating lens 44 disposed between the lens 62 and the light source 42 and the orthopedic prism 46.

The light beam generated from the light source 42 is converted into a parallel beam by the collimating lens 44 and is incident on the shaping prism 46.

When the distance between the collimating lens 44 and the phase plate 48 is small, the orthogonal prism 46 may have a light beam passing through the collimating lens 4 to be incident on the phase plate 48 in an elliptical shape. The elliptical light beam incident therefrom serves to form a circular light beam and transmit it toward the phase plate 48.

As can be seen in FIG. 8, the phase plate 48 is configured to shift the phase incident light on the first region 49a by -θ ° and selectively shift the light on the second region 49b. The incident light is phase shifted by + θ ° so that the light intensity of either side lobe light beam is made small or hardly generated. To this end, the phase plate 48 may be arranged in parallel with each other in the tangential direction (ie, parallel to the track) on the front surface of the electro-optical device whose light transmittance varies depending on the liquid crystal substrate or other applied voltage as shown in FIG. 9. The second electrodes 48a and 48b and the common electrode 48c facing the first and second electrodes 48a and 48b are coated. A negative voltage is applied to the first electrode 48a to shift the incident light incident on the first region 49a by -θ °, and a positive voltage is applied to the second electrode 48b to apply the first region 49a. The incident light incident on the?) Is shifted by + θ °. At this time, if the voltage levels applied to the first and second electrodes 48a and 48b are varied, the amount of phase shift can be adjusted. The applied voltages of the first and second electrodes 48a and 48b are switched by a controller to be described later to phase-shift any one of side lobes generated on both sides of the main lobe. In fact, when the incident light beam is shifted -45 ° out of phase in the first region 48a and + 45 ° out of phase in the second region 48b, the light intensity of the micro light spot focused on the optical disk 31 is shown in FIG. As can be seen, the left side lobe 71b of the main lobe 71a is approximately 4 × 10 ⁻² (W / cm ² ), while the right side lobe 71b is approximately 4 × 10 ⁻² (W / cm ² ). Is observed.

The beam splitter 50 transmits the light beam incident from the phase plate 48 toward the objective lens 62, and reflects the reflected light beam reflected from the optical disk 31 toward the sensor lens 62.

The objective lens 52 serves to focus the light beam incident from the beam splitter 50 as a light spot on the recording surface of the optical disc 1. As for the micro light spot focused from the objective lens 52, the diameter of the main lobe 71a becomes narrow in the track crossing direction (radial direction) by the phase plate 48 as shown in FIG. 10, and only one side lobe 71b is used. It exists. The main lobe 71a is reduced in diameter across the track compared to the general light spot 20 to follow the track centerline and irradiate the pits 31a. The side lobe 71b is a phase shifted by the control unit described later in the first region 48a or the second region 48b in the phase plate 48 so that the side lobe 71b is parallel to the main lobe 71a in the track crossing direction. The track space on the wide pitch side is irradiated. That is, when the main lobe 71a is irradiated to the pits 31a, the side lobe 71b irradiates only the mirror area. At the time of reproduction, the light beam reflected from the optical disc 31 is irradiated to the sensor lens 62 via the objective lens 52 and the beam splitter 50. Then, the sensor lens 62 focuses the incident light beam on the photodetector 60, and the photodetector 60 converts the received signal into an electrical signal. At this time, the reflected light beam of the side lobe 71b does not affect the reflected light beam of the main lobe 71a at the mirror region level.

On the other hand, the micro light spot controlled by the phase plate 48 has almost no side lobe 71b component, but any of the micro light spots is an asymmetric super resolution light spot based on the track transverse direction (radial direction). Can be applied.

Fig. 11 is a diagram showing an apparatus for reproducing an optical recording medium according to an embodiment of the present invention.

In FIG. 11, a detailed description of the optical pickup apparatus will be omitted.

In the configuration of Fig. 11, the reproducing apparatus of the optical recording medium according to the present invention performs signal processing on the signal converted from the photodetector 60 to derive the reproducing signal and to detect information indicating the position of the wide track pitch Tpw. The reproduction signal processing unit 72 and a control unit 74 for driving the phase plate 48 in accordance with the information detected from the reproduction signal processing unit 72 are provided.

The reproduction signal processing unit 72 derives the reproduction signal and the servo signal by using the signal converted from the photodetector 60 and provides information indicating the presence position of the wide track pitch Tpw from the signal converted by the photodetector 60. It detects and supplies it to the control part 74.

The control unit 74 switches the driving of the first electrode 48a and the second electrode 48b of the phase plate 48 in accordance with the information input from the reproduction signal processing unit 72 to change the generation position of the side lobe 71b. Control. In addition, the controller 74 controls the phase shift amount by varying the driving voltage levels of the first and second electrodes 48a and 48b.

On the other hand, the method for controlling the side lobe 71b to be irradiated to the wide track pitch Tpw, as described above, writes the information previously committed to the optical disc 31 once per rotation or by the sensor means. The phase plate 48 may be controlled according to the detection signal by sensing the crosstalk left / right generation amount.

As described above, the high density optical recording medium according to the present invention has a track structure of different track pitches, and the sum of the wide track pitch and the narrow track pitch is smaller than the sum of the general track pitches to have a high density recording capacity and cross. The light beam of the torque component is irradiated to the wide track pitch side, making it suitable for crosstalk reduction. The optical pickup apparatus and the reproduction method using the optical pickup apparatus according to the present invention generate an asymmetric light beam with respect to the transverse track direction and control the light beam of the crosstalk component to be irradiated toward the wide track pitch, thereby effectively reducing crosstalk and accurately reproducing it. You get a signal.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a view showing a conventional optical pickup device.

2 is a view showing in detail the light modulator shown in FIG.

3 is a characteristic diagram showing the light intensity of a conventional super resolution light spot.

FIG. 4 is a diagram showing a state in which an optical spot having the light intensity characteristic of FIG. 3 is irradiated to the optical recording medium. FIG.

5 shows an optical recording medium according to an embodiment of the present invention.

6 is a voltage waveform diagram showing a motor driving voltage.

7 is a view showing an optical pickup apparatus according to an embodiment of the present invention.

8 is a diagram illustrating phase modulation characteristics of the phase plate shown in FIG. 7.

FIG. 9 is a plan view (A) showing the detailed structure of the phase plate shown in FIG. 7 and a longitudinal cross-sectional view (B) cut along the line "A-A". FIG.

FIG. 10 is a view showing a state in which a super resolution light beam generated by phase modulation of the phase plate shown in FIG. 7 is irradiated to an optical recording medium having track structures of different track pitches. FIG.

Fig. 11 is a diagram showing an apparatus for reproducing an optical recording medium according to an embodiment of the present invention.

FIG. 12 is a light intensity characteristic diagram of an asymmetric super-resolution light beam generated when the phase plate shown in FIG. 7 is subjected to phase modulation of an incident light beam by 45 °. FIG.

<Brief description of symbols for the main parts of the drawings>

1,31: optical disc 1a, 31a: ft

2,42 light source 4,44 collimator lens

6:46 Orthopedic Prism 8: Light Intensity Modulator

10,50: beam splitter 12,52: objective lens

14: reproduction signal detection system 21a, 71a: main lobe

21b, 71b: side lobe 60: photodetector

62: sensor lens 72: playback signal processing unit

74: control unit

Claims (15)

An optical recording medium for recording / reproducing information by using light, A structure in which tracks on which information is recorded are alternated with at least two different track pitches; And information for identifying the different track pitches is recorded. The method of claim 1, The different track pitches may include a first track pitch; And a second track pitch wider than said first track pitch. The method of claim 2, And the first and second track pitches alternate per revolution. The method of claim 2, And information for identifying the first and second track pitches once per rotation in correspondence with the first and second track pitches. An optical pickup apparatus comprising a condensing optical system for condensing a light beam from a light source on a recording medium and a light receiving optical system for receiving a light beam reflected from the recording medium, An optical pickup device disposed on an optical path of the condensing optical system and provided with a light beam of super resolution by modulating the light beam intensity or phase from the light source and having an asymmetric light beam of the super resolution; . The method of claim 5, wherein And the optical modulator modulates the incident light beam such that the light beam of the super resolution has an asymmetric shape with respect to the track direction. The method of claim 5, wherein And the optical modulator modulates the incident light beam to suppress the light beam of one side lobe component in the super resolution light beam. Providing an optical recording medium having a structure in which tracks on which information is recorded are alternated with at least two different track pitches; Detecting a signal by irradiating the optical recording medium with an asymmetric super-resolution light beam based on a track crossing direction; Determining a positional relationship of adjacent tracks based on the detected signals; And reproducing a reproduction signal by adjusting the asymmetry of the super resolution light beam according to the determined positional relationship. The method of claim 8, And recording the information for identifying the different track pitches on the optical recording medium. The method according to claim 8 or 9, And the positional relationship of the adjacent tracks is determined by the information. The method of claim 8, And the positional relationship between the adjacent tracks is determined by detecting a noise component included in the reproduction signal. An apparatus for recording or reproducing a recording medium having a structure in which tracks on which information is recorded are alternately arranged with at least two different track pitches, An optical pickup for collecting a light beam from a light source on the recording medium and receiving a reflected light beam; A signal processor for signal-processing and outputting the signal detected and converted by the optical pickup; A control unit for controlling the optical pickup in accordance with a signal output from the signal processing unit; And the signal processor detects information for identifying the different track pitch among the signals detected by the optical pickup, and the controller controls the optical pickup according to the detected information. The method of claim 12, And the control unit controls driving position of the side lobe by switching the driving of the optical pickup according to the information output from the signal processing unit. The method of claim 13, And a generation position of the side lobe is controlled by switching the driving of the first electrode tube second electrode of the phase plate included in the optical pickup. The method of claim 12, And the controller controls the amount of phase shift by varying the driving voltage level of the optical pickup.