KR100400544B1 - Lens for optical recording and reproducing system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens for an optical recording and reproducing system, wherein an incident surface on which light generated from a light source is incident, a first reflection surface on which light passing through the incident portion is reflected, and light reflected from the first reflection surface And a second reflecting surface to reflect, wherein the incident surface is formed of a Schmitt collector surface, the second reflecting surface is a spherical surface, and the first reflecting surface and the second reflecting surface are coated with a reflective material. And a lens for a reproduction system. According to the present invention, by providing an optical system having a very small size and weight, it is possible to record and reproduce information using only a focusing lens without an objective lens, and to provide an ultra-thin optical recording and reproducing system which significantly reduces the overall height of the system. have.

Description

Lens for optical recording and playback system {LENS FOR OPTICAL RECORDING AND REPRODUCING SYSTEM}

The present invention relates to an optical system for an optical recording and reproducing system, and more particularly, to an optical system for an optical recording and reproducing system capable of reducing the thickness and volume of a lens and recording ultra-high density information.

An optical recording medium or a magneto-optical recording medium must have a small bit (or recording mark) size and a narrow track width to have a high density recording capacity. However, since the spot size of the light condensed on the recording medium to form a bit in the recording film of the recording medium is limited by the diffraction limit, there is a limit in improving the recording density.

In light of the trend of large-capacity information, new optical recording / reproducing methods are required to overcome the limitations of existing optical recording / reproducing methods. In recent years, research on near field recording / reproduction using near field, which is expected to significantly improve recording capacity, has been increasing.

The principle of near field optical recording and reproduction is as follows. Light entering the lens at an angle greater than or equal to the critical angle is totally reflected when traveling from a dense refractive index to a small one. At this time, due to total reflection of light, light of very small intensity exists on the surface of the lens, which is called an evanescent wave or dissipation wave. The use of such evernet wave enables high resolution, which is impossible due to the absolute limit of resolution due to diffraction of light in the far-field, that is, the diffraction limit. The near field optical recording and reproducing optical system totally reflects the light in the lens to generate an Evernet wave on the surface of the lens, and records and plays back by coupling the Evernet wave and the recording medium.

1 is a perspective view showing a conventional near field optical recording system 10. In the deck 18, a central portion of the disk 11, which is a recording medium, is mounted on the spindle motor (not shown) so as to be rotatable, and a recording and reproducing apparatus is provided on the other side of the inside. The floating head slider 12 is supported by the suspension arm 14 on the upper surface of the disk, and one side of the suspension arm is connected to the pickup 17. A voice coil motor (VCM) 16 is installed below the pickup to allow the pickup to rotate at an angle within a certain range. On the other hand, a fixed arm 13 is supported on the upper surface of the head slider from the pickup, and a prism 15 is provided at the end of the fixed arm. Light generated by the light source (not shown) of the pickup part is changed in the prism, passes through a lens (not shown) mounted on the head slider, and finally enters the disk surface. It is possible to record or reproduce the optical information by the interaction of the incident light with the disk surface.

FIG. 2 is an enlarged schematic view of an optical system mounted on a head slider in the system of FIG. 1, which is composed of a hemispherical solid immersion lens (SIL) 22 and a primary condenser lens 21. The SIL is spherical in shape with a top surface spherical and a bottom surface flat, and is installed so that the center of the flat portion of the SIL coincides with the focal point of the primary condensing lens. In the center of the lower plane of the. In order to record data (bits) on the disc using the SIL, as shown in FIG. 2, the SIL is brought close to the surface of the recording medium 23 at very small intervals, for example, at intervals of about 10 to 70 nm. In this proximity, an optical near field phenomenon occurs in which a part of the primary energy focused on the lower surface of the SIL is transferred to the recording medium. This near field phenomenon makes it possible to record or reproduce data on the recording medium surface. For example, the energy delivered from the SIL heats part of the surface of the record carrier, causing local phase changes. This phase change forms bits on the surface of the recording medium. That is, to record information. When reading the recorded information, the property of reflectance is changed at the locally changed phase. When light of low intensity is incident through the SIL, and the intensity of the light reflected from the surface of the recording medium and output through the SIL is measured by the optical sensor, the reflectance varies depending on the presence or absence of the bit, so that information can be read.

As described above, in the optical system using the SIL, it is possible to overcome the diffraction limit of the light and reduce the light spot, but there are the following problems.

In general, an optical lens generates an aberration in which light does not collect at a point, and this aberration has a characteristic that the higher the magnification of the lens is, the larger it becomes. Since an optical system using SIL requires a large-scale primary condenser lens, the aberration of the primary condenser lens greatly degrades the primary condensing performance of the optical system.

In addition, the data recording / reproducing apparatus using SIL requires a primary condenser lens, which makes the device bulky and complicated, and makes it difficult to assemble the entire data storage device and the primary condenser lens. In particular, there is a limit in reducing the height of the head slider on which the lens is mounted, and it is difficult to manufacture an ultra-thin optical recording and reproducing system that can be mounted on a portable device or the like.

An object of the present invention is to reduce the volume and thickness occupied by the optical system to facilitate assembly of the optical system and the entire system, and to enable an ultra-thin optical recording and reproducing system.

It is also an object of the present invention to provide an optical system for an optical recording system capable of recording and reproducing with only a focusing lens without a focusing lens.

Other objects and features of the present invention will appear in detail from the following specific examples and claims.

1 is a perspective view showing a conventional near field optical recording system.

FIG. 2 is an enlarged schematic view of an optical system mounted to a head slider in the system of FIG. 1.

Figure 3a is a schematic diagram showing a spherical reflector eliminated spherical aberration using the Schmitt corrector.

3B is a schematic diagram showing the principle of the present invention.

Figure 4a is a cross-sectional view showing an embodiment of the present invention.

4B illustrates an embodiment in which the position of the lens of FIG. 4A is modified.

4C is a view illustrating a lens in which a step is formed in a focus as another embodiment of the present invention.

5A to 5C show still another embodiment of the present invention, in which a hologram is provided in front of a lens entrance surface, respectively.

6 shows another embodiment of the present invention in which a prism is provided in front of a lens entrance surface.

7 is a schematic diagram showing an optical recording system equipped with a lens of the present invention.

*** Explanation of symbols for main parts of drawing ***

30a: Spherical surface (second reflecting surface) 30b: Schmidt corrector surface (incident surface)

30c: Lens bottom (first reflecting surface) C: Focus of lens

In order to achieve the above object, the present invention provides an incident surface on which light generated from a light source is incident, a first reflecting surface on which light passing through the incident part is reflected, and a second panel reflecting light reflected from the first reflecting surface again. A lens for an optical recording and reproducing system including an inclined surface, wherein the incidence surface is formed of a Schmitt collector surface, the second reflection surface is a spherical surface, and the first reflection surface and the second reflection surface are coated with a reflective material. To provide.

The incident light forms a focal point on the first reflective surface, and it is also possible to change the shape of the incident surface, which is a Schmitt collector surface, so that the focal point is formed below the first reflective surface.

The optical system of the present invention is applicable not only to the optical recording and reproducing system using the near field, but also to the system using the existing far-field.

The lens of the present invention utilizes the principle of Schmidt Corrector. Spherical aberration is a phenomenon in which when light incident in parallel to the optical axis passes through the lens, the light passing through the periphery of the lens focuses at a shorter distance than the light passing through the center of the lens. The surface of the lens is spherical. This is one of the defects that occur during imaging. The Schmitt corrector is a correcting lens for correcting spherical aberration.

Referring to FIG. 3A, the spherical reflector can be seen by removing the spherical aberration by placing the Schmitt corrector 32 in front of the spherical reflector. Light 35 incident on the spherical reflector 30 converges to the focus C inside the reflector. The center portion 32a of the Schmitt corrector becomes convex in the incident direction of the light, so that the incident beam is narrowed, and the edge 32b is concave in the incident direction of the light, and the incident beam diverges. Therefore, the spherical aberration caused by the spherical mirror is eliminated and the incident beams all converge at the focal point.

The Schmitt corrector is for removing the aberration generated in the spherical lens or spherical mirror, the shape can be changed according to the shape of the lens or mirror surface.

Figure 3b is a schematic diagram showing the principle of the present invention, in the spherical reflector of Figure 3a shows a hemisphere corresponding to the base of the inclined axis (y) passing the focal point (C) and at a certain angle with respect to the central axis (x) have. 3a, unlike light incident in parallel with the central axis x of the spherical mirror 30, the light 35 is incident at one end of the spherical mirror (upper part in the drawing). . The underside coats the reflective material to reflect the incident beam. The incident light is symmetrical to the light indicated by the dotted line in the figure (light passing through the Schmitt corrector) with respect to the inclined axis y, and a focus is formed at the same point as in FIG. 3A.

An embodiment of the present invention employing the Schmitt corrector described in FIGS. 3A and 3B is shown in FIG. 4A. The present embodiment shows a lens in which the upper surface 30a of the lens is a spherical surface, the lower surface 30c is a flat surface, and the Schmitt collector surface 30b is formed at a site where light is incident. The lower surface 30c of the lens corresponds to the first reflection surface, and the upper surface 30a of the lens corresponds to the second reflection surface. The bottom and top of the lens are coded with reflective material.

The Schmitt collector surface prevents the light from collecting at one point by spherical aberration when the incident light reaches the upper surface of the lens, that is, the spherical surface, is reflected and focused at the focal point C. Thus, the light incident from the light source converges very little on the focal point, theoretically close to zero. In addition, it is possible to reduce the light loss and to enable a large numerical aperture.

FIG. 4B is a cross-sectional view illustrating a lens in which the position of the lens illustrated in FIG. 4A is modified, and the surface where the focus C of the lens is located is horizontal to the bottom surface. In an actual optical recording system, it is preferable to install in the head in such a position. This is because the bottom surface of the lens on which the focal point is formed is easily close to the recording medium. The lens of the present invention as shown can make a small spot light with only one focusing lens without a separate objective lens. In addition, the height of the lens is very low, preferably 0.3 mm or less, which enables an ultra-thin system that significantly reduces the thickness of the entire optical recording system. In addition, the lens of the present invention can directly enter light into the incidence portion without the need for a conversion means such as a prism for changing the path of light to enter the incidence portion of the lens from the light source, so that the height of the head portion on which the lens is mounted and The weight can be reduced, and thus the load of the driving means for driving the head can be reduced.

4C illustrates an embodiment in which the step 40 is formed in the focal portion of the lens. The formation of a step can prevent optical interaction between the non-focus portion and the recording medium at the bottom of the lens, thereby adversely affecting recording and playback, and the optical interaction between dust and other contaminants between the lens and the recording medium. It can prevent the interruption. The material forming the step must be a transparent material through which light can pass, and the step is preferably formed at about 0.1 to 100 nm so as not to interfere with the recording and reproduction of the information. On the other hand, it is possible to further reduce the spot size of the focused light by aperture coating on the focus portion.

5A to 5C illustrate embodiments in which holograms h1, h2, and h3 are provided in front of an entrance surface of a lens as another embodiment of the present invention. In the embodiment of FIG. 4A, the light incident on the Schmitt collector surface is inclined, and the hologram is installed in front of the lens incidence surface so that the inclined light is incident on the lens using a parallel beam generated from a light source. . In addition, the hologram is advantageous in that the margin of tolerance can be increased because the diffraction angle and the wave front aberration of the light incident on the incident surface can be adjusted. The hologram may be modified in various forms in addition to the embodiment shown in FIGS. 5A to 5C. In addition, as shown in the embodiment of Figure 6, it is also possible to adjust the incident angle of the incident beam by installing the prism (P) in front of the incident surface of the lens instead of the hologram.

7 is a schematic diagram showing an optical recording system equipped with a lens of the present invention. Although the size of the lens is shown relatively large, it is actually mounted on the head (not shown) in a very small size in the system. Since the size and weight of the lens is very small, the servo of the lens is very easy in the present system, and the lens of the present invention can be applied to both the integrated pickup and the separate pickup. In addition, in order to mount the lens of the present invention, the head of the hard disk can be used as it is, thereby reducing access time.

According to the present invention, by providing an optical system having a very small size and weight, it is possible to record and reproduce information using only a focusing lens without an objective lens, and to provide an ultra-thin optical recording and reproducing system which significantly reduces the overall height of the system. . In addition, the weight of the head portion can be reduced, and the incident pupil of the light source can be made small, so that power consumption of the driving means and the system as a whole can be greatly reduced.

Claims (7)

An incident surface to which light generated from the light source is incident, A first reflecting surface on which light passing through the incident part is reflected, And a second reflecting surface for reflecting light reflected from the first reflecting surface again, The incident surface is formed of a Schmitt collector surface, the second reflecting surface is a spherical surface, the first reflecting surface is a plane, the focal point where the incident light converges, and the first reflecting surface and the second reflecting surface are reflective materials. Coated lenses for optical recording and playback systems. delete The lens for an optical recording and reproducing system according to claim 1, wherein a step is formed below the first reflection surface on which the focal point is formed. The lens of claim 3, wherein the size of the step is 0.1 to 100 nm. A lens for an optical recording and reproducing system as set forth in claim 1, wherein the incident light forms a focal point below the first reflecting surface. The lens of claim 1, further comprising a hologram that changes the path of light incident from the light source to the incident surface. The lens of claim 1, further comprising a prism for changing a path of light incident from the light source to the incident surface.