KR20090028904A - Information storage device - Google Patents

Abstract

An information storage medium including negative refraction layers is provided to minimize the movement of actuator for recording of different layer and compensate for spherical aberration within the information storage medium. An information storage medium comprises a protective layer(32) which is laminated on the top of the storage medium for protection, a plurality of recording layers(33,34,35) for recording data with the light passing through a lens(31), space layers(36,37) which occupy a predetermined space between the recording layers and exhibit insulation and reflection effect, and negative refraction layers(38,39) made of a material having negative refraction modulus and laminated on one side of the recording layer or the space layer in order to negatively refract the light at the boundary surface.

Description

Information storage medium {INFORMATION STORAGE DEVICE}

1 is a view showing a state in which a lens and an actuator move for recording on different recording layers in an information storage medium having several recording layers.

2A and 2B illustrate a general refraction phenomenon and a negative refraction phenomenon according to an embodiment of the present invention.

3 is a view for explaining a focusing path of light in an information storage medium including a negative refractive layer according to an embodiment of the present invention;

4 is a view showing a three-dimensional structure of the negative refractive layer in accordance with an embodiment of the present invention.

5 is a cross-sectional view of the negative refractive layer according to the embodiment of the present invention.

6 is a diagram illustrating that a negative refractive layer compensates for spherical aberration according to an embodiment of the present invention.

  ※ Description of the main parts of the drawing ※

32: protective layer 33, 34, 35: recording layer

36,37: space layer 38,39: negative refractive layer

41 bubble 42 gallium arsenide (GaAs)

The present invention relates to an information storage medium in which a negative refractive layer having a negative refractive property is additionally inserted in an information storage medium having a plurality of recording layers.

As the amount of information to be processed increases rapidly with industrial development, there is a demand for an optical recording medium having a high recording density. Such a high capacity optical recording medium can be realized by reducing the size of the optical spot focused on the recording medium. In order to reduce the size of the light spot, light having a short wavelength must be used, and the numerical aperture NA of the objective lens must be increased.

Alternatively, as another method for increasing the storage capacity, an information storage medium having a plurality of recording layers is used. In an information storage medium having a plurality of recording layers, transparent substrates are formed on the upper and lower surfaces of the information recording layer to protect the recording layer from dust and external scratches. In addition, a storage medium having a plurality of recording layers separates the two recording layers by placing a space layer between adjacent recording layers.

As described above, in an information storage medium having a plurality of recording layers, various methods are used for recording and reproducing information of a plurality of recording layers. Generally, a method of adjusting the light condensing position by moving an actuator is used. .

However, this method has a burden of moving the actuator by the distance between the spatially separated recording layers.

Fig. 1 shows a state in which an actuator moves for recording on different recording layers in an information storage medium having several recording layers.

The information storage medium of FIG. 1 includes several recording layers 13, 14, 15 and 16, space layers 17, 18 and 19 and a protective layer 12. As shown in FIG. At this time, the light passing through the lens 11 is focused on the recording layers 13, 14, 15, and 16 for recording the information.

However, in the case of the storage medium provided with several recording layers 13, 14, 15, and 16 as described above, a lens 11 for condensing light for recording on different recording layers and an actuator (not shown) for driving the same Should move by the distance between recording layers.

The left part of FIG. 1 shows a state in which light is focused on the second recording layer 14 for recording on the second recording layer 14. In this state, in order to record on the fourth recording layer 16 separated by 'a', the lens 11 for focusing light and the actuator for driving the same must also move vertically by 'a' in the fourth recording layer 16. Can be condensed into (Figure 1 right).

As described above, for recording in different recording layers, the moving distance of the lens and the actuator is increased. However, this causes structural stability problems of the information storage device and increases power consumption.

In addition, in the information storage medium, a spherical aberration problem occurs along each path of the focused light, and additionally, elements for compensating for this problem must be provided.

As described above, additional elements for compensating spherical aberration may inevitably complicate the information storage device.

Accordingly, an object of the present invention is to propose an information storage medium capable of minimizing a moving distance of an actuator and compensating spherical aberration by appropriately inserting a refraction layer in an information storage medium having a plurality of recording layers. .

The present invention relates to an information storage medium.

More specifically, the information storage medium according to the present invention is stacked on top of the storage medium to protect the storage medium, a plurality of recording layers used to record data by condensing the light passing through the lens, the recording layer A space layer that occupies a predetermined space therebetween and insulates and reflects, and comprises a material having a refractive index, which is stacked on one surface of the recording layer or the space layer and includes a negative refractive layer that negatively refracts light at an interface thereof. do.

More preferably, the negative refraction layer includes gallium arsenide (GaAs) filling the space between the bubbles and the space arranged at a predetermined interval, the bubble has a planar cubic lattice (FCC) structure.

More preferably, the negative refractive layer is laminated between one of the recording layers and the space layer or below the lowest recording layer of the recording layers.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily understand and implement the same.

2A and 2B illustrate general refraction and negative refraction according to an embodiment of the present invention.

The negative refraction phenomenon used in the present invention is a phenomenon in which light is refracted in a direction opposite to that of light in a general material having a positive refractive index when the light is incident on an artificial medium having a negative refractive index. .

Negative refractive index means that both permittivity and permeability have negative values.

Most materials have positive permittivity and permeability. However, since the late 1960s, we have been studying materials with negative permittivity and negative permeability, which have opposite directions of phase velocity and group velocity, thus making left-handed materials: LHM).

At the interface between the right-handed materials (RHM), which is a common material, and the left-handed material, electromagnetic waves are deflected in a direction opposite to the existing direction. When the electromagnetic wave emitted from the point light source is applied to the flat plate of the left-handed material, Focused at one point inside.

2A is a diagram illustrating a general refractive phenomenon. In Fig. 2A, the media 21 and 22 are both made of a material having a positive refractive index. However, since the magnitude of the refractive index is different, the light is refracted at the interface.

That is, according to Snell's law, if the refractive index of the upper medium 21 is n1, the refractive index of the lower medium 22 is n2, the incident angle is θ1, and the refractive angle is θ2, then "n1 x sin θ1 = n2 x sin θ2". The relationship is established.

2B is a diagram illustrating a negative refraction phenomenon according to an embodiment of the present invention. In FIG. 2B, the upper medium 23 is made of a material having a positive refractive index while the lower medium 24 is made of a material having a negative refractive index.

The material having the negative refractive index will be described in detail later, and as shown in FIG. 2B, the boundary between the material having the positive refractive index and the material having the negative refractive index does not have the general refractive direction as shown in FIG. do. This is called a negative refractive phenomenon, which is the same when the upper medium 23 is a material having a negative refractive index and the lower medium 24 is a material having a positive refractive index.

That is, the negative refractive phenomenon occurs at the interface between a material having a positive refractive index and a material having a negative refractive index.

3 is a view for explaining a light converging path in an information storage medium including a negative refractive layer according to an embodiment of the present invention.

An information storage medium according to an embodiment of the present invention includes a lens 31 that focuses light, a protective layer 32 that is stacked on top of the storage medium to protect the storage medium, and light passing through the lens is focused to record data. And a plurality of recording layers 33, 34, and 35 used to occupy a predetermined space between the recording layers, the space layers 36 and 37 for insulating and reflecting, and materials having a negative refractive index. Negative refractive layers 38 and 39 that negatively refract light at an interface with a layer of refractive index material.

In the present specification, a hierarchical structure as illustrated in FIG. 3 is described for explanation, but the structure may be modified in various ways. For example, the stacking order of the space layer and the negative refractive layer may be reversed, and there may be only the space layer, only the negative refractive layer, and the space layer and the negative refractive layer may be stacked between the recording layer and the recording layer. have.

3 illustrates three types of light for the purpose of illustrating the present invention. The first light L1 (dotted line) is incident on the first negative refractive layer 38 through the protective layer 32, the first recording layer 33, and the first space layer 36. In this case, since the first space layer 36 is a material having a positive refractive index and the first negative refractive layer 38 is a material having a negative refractive index, a negative refractive phenomenon occurs at the interface between the two layers 36 and 38.

As a result of the negative refractive phenomenon, refraction occurs in a direction opposite to the traveling direction of the light, and as a result is focused on the spot of the second recording layer 34 to store the information. And it is necessary to adjust the thickness of each layer so as not to focus on the other recording layers.

The second light L2 (solid line) is an optical path when the lens and the actuator move slightly downward than the first light L1. In this case, the second light is immediately focused on the spot of the first recording layer 33 to store the information. Even in this case, it is necessary to adjust the thickness of each layer so as not to focus on the other recording layers.

The third light L3 (dashed line) is an optical path when the lens and the actuator slightly move downwards than the second light L2. The third light L3 is incident on the first negative refractive layer 38 through the protective layer 32, the first recording layer 33, and the first space layer 36. In this case, since the first space layer 36 is a material having a positive refractive index and the first negative refractive layer 38 is a material having a negative refractive index, a negative refractive phenomenon occurs at the interface between the two layers 36 and 38.

As a result of the negative refractive phenomenon, refraction occurs in a direction opposite to the traveling direction of the light and passes through the first negative refractive layer 38. Light enters the second recording layer 34 again, where the first negative refractive layer 38 is a material having a negative refractive index, and the second recording layer 34 is a material having a positive refractive index. Negative refraction occurs again.

Thus, a negative refractive phenomenon occurs in the second recording layer 34, and the third light L3 is refracted in the opposite direction to proceed, and consequently is focused on the spot of the third recording layer 35 to store the information. Even in this case, it is necessary to adjust the thickness of each layer so as not to focus on other recording layers.

In Fig. 3, the length between the plurality of recording layers 33, 34, 35 is 'a', but the lens and actuator have moved only by 'b'. Compared to the conventional method in which the lens and the actuator had to move by 'a' in order to record information on the recording layer separated by 'a', the moving distance of the lens and the actuator was significantly reduced.

4 is a view showing the structure of the negative refractive layer according to an embodiment of the present invention.

The negative refractive layer according to the embodiment of the present invention includes a space 41 spaced at regular intervals and a gallium arsenide (GaAs) 42 filling the space between the bubbles. As shown in FIG. 4, the bubbles 41 are spaced at regular intervals in a three-dimensional space, and more specifically, have a face-centered cubic (FCC) structure.

5 is a cross-sectional view of the negative refractive layer in accordance with an embodiment of the present invention. The negative refractive layer includes bubbles 41 spaced at regular intervals and gallium arsenide 42 filling the space between the bubbles.

The diameter of the bubble and the refractive index of gallium arsenide used in the present invention are determined according to the wavelength of the light used to record the information. For example, when the information is recorded using 500 nm visible light, the diameter of the bubble is 300 nm. The refractive index of gallium arsenide has a value of 3.24-3.50. Therefore, the structure of the negative refractive layer may vary depending on the wavelength of light used for recording the information.

6 is a view for explaining the principle that the negative refractive layer compensates for spherical aberration according to an embodiment of the present invention.

Spherical aberration is an aberration that occurs because a shop made from a beam of light from a point on the optical axis depends on which part of the lens the beam has passed. In order to compensate for such spherical aberration, a conventional compensation element is provided. However, in the present invention, the spherical aberration is compensated for by using the structure of the negative refractive layer.

If the spherical aberration is not compensated for, the light focused on the recording layer will bleed. If a blur occurs, accurate recording and reproducing of the information cannot be performed.

The path in which the light moves in the medium may be moved in the vertical direction 61 or may be moved in the diagonal direction 62. In this case, if the refractive index in the moving path is n and the moving distance is d, the value of n × d must be constant in any path in the medium. Compensating spherical aberration makes the value of n × d constant.

That is, in FIG. 6, since the moving distance d2 in the diagonal direction is larger than the moving distance d1 in the vertical direction, the refractive index n2 on the moving path in the diagonal direction is the refractive index in the vertical direction in order to establish the above equation. It must be smaller than (n1).

To this end, looking at the structure of the negative refractive layer, which is a face-centered cubic structure, through FIG. 6, it is confirmed that the gas is subjected to a lot of bubbles having a small refractive index when proceeding in the diagonal direction, and that the gallium arsenide having a large refractive index is passed when proceeding in the vertical direction. Can be.

In this way, spherical aberration can be compensated for by appropriately inserting the negative refractive layer in the information storage medium of the multi-recording layer.

In the present specification, only the structure and the constituent material of the negative refractive layer are illustrated as described above for the purpose of illustration, and the scope thereof is not limited to this example and may be replaced by any other material having an equivalent role.

So far, the present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be implemented.

Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

By providing a negative refractive layer in the conventional hierarchical structure of the information storage medium as described above, the movement distance of the actuator can be greatly reduced when storing information in a plurality of recording layers, and by compensating spherical aberration through the structure of the negative refractive layer By eliminating spherical aberration compensating elements, a more compact information storage device can be manufactured.

Claims (5)

A protective layer laminated on top of the storage medium to protect the storage medium; A plurality of recording layers used to record data by condensing light passing through the lens; A space layer occupying a predetermined space between the recording layers, and having an insulating and reflective function; And A negative refractive layer composed of a material having a negative refractive index and stacked on one surface of the recording layer or the space layer to negatively refract light at its interface. Information storage medium comprising a. The method of claim 1, The negative refractive layer is an information storage medium comprising gallium arsenide (GaAs) filling the space between the bubbles and the space arranged at a predetermined interval. The method of claim 2, And said bubble forms a face-centered cubic lattice (FCC) structure. The method of claim 1, And the negative refractive layer is laminated between one of the recording layers and the space layer. The method of claim 1, And the negative refractive layer is stacked below the lowest recording layer of the recording layer.

Images