KR20000061708A - optical pick-up system using near-field - Google Patents

Abstract

PURPOSE: An optical pickup system using a near field, is provided to maintain a regular-sized optical spot on a surface of a protective layer, and an optimal optical spot on an information recording surface, even though the protective layer is thick, by use of a solid immersion lens in order to prevent contamination. CONSTITUTION: The optical beam from a light-transceiving part(10) and a reflective mirror(12) are incident to an objective lens(24), which emits the optical beam to a solid immersion lens(SIL,26). The optical beam emitted is reflectively incident in a form of emitting to a surface of a solid immersion mirror(SIM,26). The reflective optical beam has a larger angle than an emitted angle, via a first and second reflective surface, to be emitted to an emission surface of the SIM. The optical beam emitted to the SIM, forms an optical spot at a center of an information recording surface. The optical spot creates a near field between a surface opposite a disc(28) and protective layer(283) thereof. The creation results in recording information on the disc or reading the information therefrom. And then the optical spot is remained 0.3 mm on a surface of the disc which is facilitated to be proof against stains and dust, and the near field enables recording information in high-density.

Description

Optical pick-up system using near-field

The present invention relates to an optical pickup system using a near field.

A conventional optical pickup system using a near field for increasing the recording capacity of an optical recording / reproducing apparatus will be described with reference to FIG.

The optical pickup system shown in FIG. 1 includes a transmitter / receiver 10, a reflection mirror 12, an objective lens 14 for condensing, a solid immersion lens 16, and a disk 18. Here, the disk 18 is composed of an information recording layer 181 and a protective layer 183, and the thickness of the protective layer 183 is approximately 20 nm. The transmitter / receiver 10 emits a light beam having a diameter optimized for the objective lens 14 to the reflection mirror 12, and the reflection mirror 12 transmits the light beam emitted from the transmitter / receiver 10 toward the objective lens 14. Reflect. The objective lens 14 condenses the light beam incident from the reflecting mirror 12 to the SIL 16, and the light spot condensed at the SIL 16 is a surface facing the disk 18 and a protective layer of the disk 18. A near field is formed between 183. As a result, information is recorded on the disk 18 through the near field or information is read from the disk 18. Here, the objective lens 14 and the SIL 16 are supported by a servo system, and the objective lens 14 is provided by a servo system which receives an error signal for focusing and tracking from a signal received by the transmitter / receiver 10. Driven, the SIL 16 is lifted aerodynamically from the disk 18 by the servo system. An air gap having an interval within one wavelength length of light is formed between the SIL 16 and the disk 18.

However, in the conventional optical pickup system that generates the near field as described above, it is possible to increase the recording density, but the surface of the disk is easily contaminated with fine dust or dirt since the protective layer of the disk forms a micro layer with a thickness of about 20 nm. It was not suitable for disk removal.

An object of the present invention for solving the above problems is to use a spherical lens having a catadioptric characteristic, even if the thickness of the protective layer, which is the disk surface, the optical spot is optimal for the information recording surface, the protective layer surface of a certain size It is to provide an optical pick-up system using a near field that is resistant to contamination and maintains light spots and is also suitable for disk removal.

1 is a view for explaining a conventional optical pickup system using a near field,

2 is an optical pickup system using a near field according to an embodiment of the present invention;

3 is a detailed configuration diagram of the SIM of the system of FIG. 2;

4a-4c show the state of the light spot emitted from the SIM of the system of FIG.

5 is a view showing the state of the light spot at the same time Shanghai the objective lens of the system of FIG.

6 is a view showing a state of an optical spot when the objective lens of the system of FIG. 2 is moved left and right.

Explanation of symbols for main parts of the drawings

24: objective lens 26: SIM

28: disc 281: information recording layer

283: protective layer

The optical pick-up system using the near field for achieving the above object of the present invention is a light-receiving unit for emitting a light beam, detecting the incident light beam, optical path changing means for changing the path of the light beam, and move up, down, left and right It is located between the objective lens and the storage medium and the light incident from the light path changing means toward the storage medium, the light from the objective lens is optimal for the information recording surface irrespective of the thickness of the protective layer Condensing means having a catadioptric characteristic capable of condensing.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

2 shows an optical pickup system using a near field according to an exemplary embodiment of the present invention.

The system of FIG. 2 includes a transmitter / receiver 10, a reflection mirror 12, an objective lens 24 supported and driven by a servo system, a solid immersion mirror 26, and a disk 28. In the FIG. 2 system, disc 28 has a substrate (not shown), an optically transparent protective layer 283, and an information recording layer 281 interposed between the substrate and protective layer 283, in the form of a general disc. Has However, the protective layer 283 of the disk 28 of FIG. 2 has a thickness of approximately 110 nm or more, which is thicker than 20 nm, which is the thickness of the protective layer of a general disk. In order to form an optimal light spot on the disk, the FIG. 2 system has a SIM 26 instead of the SIL 16 of the FIG. 1 system. Of the components shown in FIG. 2 having the same reference numerals as in FIG. 1 performs the same optical function, and thus a detailed description thereof will be omitted.

The system of FIG. 2 configured as described above will be described in detail with reference to FIGS. 3 to 6.

In the FIG. 2 system, the light beam emitted from the light receiving section 10 and the reflecting mirror 12 is incident on the objective lens 24. The objective lens 24 emits a light beam incident from the reflection mirror 12 to the SIM 26. The divergent light incident from the objective lens 24 onto the SIM 26 is refracted and incident on the incident surface of the SIM 26 as shown in FIG. 3, and the incident light is incident on the first reflective surface and the first reflective surface. The light reflected from the second reflection surface and converged at an angle larger than the divergence angle is output to the exit surface. Again, the light beam emitted from the exit surface of the SIM 26 in the FIG. 2 system forms a light spot in the center of the information recording surface, which is the surface of the information recording layer 281 of the disk 28. The light spot focused on the SIM 26 forms a near field between the surface facing the disk 28 and the protective layer 283 of the disk 28. As a result, information is recorded on the disk 28 through the near field or information is read from the disk 28. At this time, the size of the light spot is maintained on the surface of the disk, which is the surface of the protective layer 283, so that the surface of the disk is resistant to contamination and dust, and the high-density recording is also possible because the information is recorded using the near field. This is because the air gap between the SIM 26 and the disk 28 is kept constant at less than one wavelength so that the near field effect is maintained aerodynamically by the servo system.

Thus, the state of the light spot emitted from the SIM 26 in order to keep the size of the light spot at 0.3 mm on the surface of the disk 28 and to concentrate the optimal light spot on the information recording surface will be described with reference to FIG.

FIG. 4A shows that the distance between the objective lens 24 and the SIM 26 is so great that a light spot is formed on the exit surface of the SIM 26. FIG. 4B is the opposite case and the objective lens 24 and the SIM 26 are reversed. The distance between them is so close that the light spot is not emitted from the exit surface and the internal reflection is generated, indicating that the light spot is not formed. FIG. 4C shows a state in which an optimum light spot is formed on the information recording surface of the disc 28 through the trial and error of FIGS. 4A and 4B. In this way, an optimal light spot is maintained on the information recording surface of the disc, and a 0.3 mm light spot is maintained on the protective layer. However, when the thickness of the protective layer is changed or the position of the disk is changed, the objective lens 24 is moved up and down as shown in FIG. 5 to maintain the light spot. In addition, when tracking is not good, the objective lens is moved left and right to maintain an optical spot. Since moving the objective lens up, down, left, and right to move the light spot is obvious to those skilled in the art, a detailed description thereof will be omitted.

Except for the SIM 26 in the above-described Fig. 2 system, the optical pickup system for DVD can be configured. This is because the objective lens 24 of FIG. 2 operates with a numerical aperture of 0.6 to focus the optimal light spot on the information recording surface of the DVD. Thus, it can be seen that the FIG. 2 system is compatible with DVD.

The present invention maintains the spot size on the surface of the disk by changing the thickness of the protective layer of the disk while performing high density recording using the near field, thereby preventing the contamination of the disk and making the disk easy to attach and detach.

Claims (6)

An optical pickup system for recording and reproducing information on a storage medium having an information recording surface and a protective layer by using a near field, A light receiving unit which emits a light beam and detects an incident light beam; Optical path changing means for changing a path of the light beam; An objective lens movable up, down, left and right and emitting light incident from the optical path changing means toward the storage medium; A condensing means positioned between the objective lens and the storage medium and having a catadioptric characteristic for condensing light from the objective lens onto an information recording surface irrespective of the thickness of the protective layer; Optical pickup system. The optical pickup system of claim 1, wherein the protective layer thickness of the disk is 110 nm or more. 3. The optical pickup system according to claim 2, wherein the objective lens moves up and down to focus light spots so as to correspond to a plurality of disks having different protective layer thicknesses, respectively. An optical pick-up system using a near field according to claim 1, wherein when the light collecting means focuses an optimal light spot on the information recording surface, the size of the light spot is maintained on the surface of the protective layer at 0.3 mm. The optical pickup system according to claim 1, wherein the condensing means comprises an incidence surface incident with divergent light from the objective lens, a first reflection surface, a second reflecting surface, and an outgoing surface for emitting convergent light. . The optical pickup system of claim 1, wherein the light collecting means is detachable and compatible with a DVD.