KR100319459B1 - Tracking method for high density near-field optical data storage and apparatus for the same - Google Patents

Abstract

The present invention relates to an optical storage method and apparatus using a near field method such as using a solid immersion lens (SIL) to store a large amount of information, and in particular, a first process of condensing and irradiating an optical signal onto an optical recording medium; ; A second step of receiving an optical signal reflecting and diffracted by the optical signal irradiated through the first process on the surface of the recording medium; A third step of comparing the diffraction amount of the optical signal received through the second step with a reference value; And a fourth process of performing a tracking operation so that the deviation of the diffraction amount of the optical signal received through the second process becomes equal to a reference value. In one embodiment, the present invention relates to a device for obtaining a tracking signal using a diffraction light detection method in a proximity type optical information storage device using a SIL, and has a simpler structure than a scan scan type which is a conventional near field tracking method. Since the push-pull method used in the conventional optical storage device can be applied, the hardware compatibility is high.

Description

Tracking method for high density near-field optical data storage and apparatus for the same

The present invention relates to a track access device and method of a near-recording optical information storage device that uses a solid immersion lens (SIL) to overcome the diffraction limit of light. The present invention relates to a tracking method and apparatus for high-density proximity optical storage for obtaining a tracking signal by diffraction light detection which detects a change in the generated optical signal with a built-in photodiode.

In general, an optical disc player for reproducing an optical disc on which digital data is recorded in an amplification manner, as shown in FIG. 1, picks up a signal for detecting a signal recorded on the optical disc 1 by generating a light source through a light emitting diode (LED). 3, a sled motor 4 for moving the pickup part 3 in the radial direction of the optical disk, a spindle motor 2 for rotationally driving the optical disk 1, A drive part 6 for driving the sled motor 4 and the spindle motor 2, a filter shape part R / F 5 for filtering the signal detected by the pickup part 3, and the pickup The driving of the drive unit 6 is controlled from the rotation error speed of the optical disk and the focus error signal FE and the tracking error signal TE output from the unit 3, and Servo unit 7 for detecting the synchronization of the output signal, the detected copper A digital signal processor (8) for restoring the filtered video signal to a digital signal and restoring the original compressed video data using a signal generator; and an amplifier unit for decoding the restored compressed video data into an output signal (OUT). (9) and a microcomputer 11 for controlling data flow between the components, and a memory 12 for temporarily storing the video data.

In general, an optical disc player having the above-described structure focuses on laser light at a point on a recording medium having magneto-optical or phase shift characteristics, and stores information to increase recording density and transmission speed and reduce connection time. Has been developed in the direction.

In other words, optical information storage devices have been developed in order to increase information storage density and to increase transfer rate and access time, so that a digital versatile disk (DVD) player can store information on multiple layers. Multi-layer recording media have resulted in commercial products capable of recording up to 4.7 Gbytes per disc.

At this time, in order to increase the recording density, it is necessary to reduce the size of the light spot focused on the recording medium. However, the limitation point has been found that the size of the focused light spot cannot be reduced below a certain size at a given wavelength due to the diffraction limit of light.

In other words, as the demand for informatization increases, the demand for information storage capacity also increases, and technologies for implementing a storage capacity of tens to hundreds of Gbytes or more and a high density of storage densities corresponding thereto have been proposed. DVD (Digital Versatile Disk) technology, near field recording technology, and the like. As the density increases in optical storage devices, tracking accuracy for high-density pits is also increased.

Therefore, in CD or DVD technology, the tracking method is mainly a method of detecting whether the pit is off the track by detecting the light returned by scanning three beams. However, in the near field optical recording technique for increasing the information storage density, the pit size is λ / 4 to λ / 10 and the track must be made dense, but it is difficult to make the dense track. Therefore, there is a need for a method of recording and reading information without a track.

SIL (solid immersion lens) method, which is the closest to the commercialization of the near field recording method recently, reduces the wavelength and increases the refraction angle when light is focused into a medium having a high refractive index, so that light is focused inside the hemispherical SIL medium and the size of the focused light spot Using a principle that can reduce to below the diffraction limit, the flat bottom surface of the SIL is close to the recording medium and the light is focused on the plane inside the SIL medium.

At this time, the focused light forms light spots of short wavelength and high NA due to the high refractive index of the SIL medium, and is transmitted on a very close recording medium with little influence of the energy diffraction of the light spot to record the information. In order to access and transmit information faster by using such a method, a method of mounting on a flying head adopted in a conventional hard disk has been proposed and studied.

In the near field recording apparatus, the conventional method uses a scanning scan type, which uses a micro moving mirror to find the direction of the track by vibrating the tracking light perpendicular to the track direction. However, this method has a disadvantage in that it is difficult to manufacture a micro moving mirror, high power consumption, and complicated device.

An object of the present invention for solving the above problems is to obtain a tracking signal by the diffraction light detection method for detecting a change in the optical signal generated when light reading and writing information diffraction by the pit with a built-in photodiode The present invention provides a tracking method and apparatus for high density near-field optical storage.

1 is a block diagram of a general optical disc player

2 is an overall apparatus diagram of a proximity optical recording apparatus using SIL proposed in the present invention.

3 is a structural diagram of a tracking device installed in the flying head at the end of the suspension in the proximity optical storage device;

4 is an exemplary view showing a form of a tracking signal detected by the signal processing of FIG.

5A to 5C are exemplary views showing shapes when the focal point is out of the center of the pit.

6 is an exemplary view illustrating a principle in which light for tracking is diffracted by interacting with a pit.

7 shows an example of the difference in the amount of light diffracted when the tracking light is out of the center of the pit.

<Explanation of symbols for the main parts of the drawings>

101: disc recording medium 102: suspension

103: rotation axis 104: light source

105: optical splitter and signal line 106: optical waveguide

107: flying head 108: signal processing device

201: incident light 202: objective lens

203: SIL 204a, 204b: diffracted light

205a and 205b: diffraction detection light 207a and 207b: diffraction signal

208: adder 209: subtractor

210: divider 211: tracking signal

212 recording medium 213 feet

301: distance axis 302: signal axis

303: tracking signal 304: positive tracking signal

305: negative tracking signal 401: tracking light

402: feet 403: feet centerline

404: tracking light centerline 501: tracking light

502: incident light 503: feet

504a and 504b: diffracted light 601: tracking light

602: tracking optical centerline

603a, 603b, 604a, 604b, 605a, 605b: diffracted light

A feature of the present invention for achieving the above object is a tracking method in an optical disc player comprising: a first step of condensing and irradiating an optical signal onto an optical record carrier; A second step of receiving an optical signal reflecting and diffracted by the optical signal irradiated through the first process on the surface of the recording medium; A third step of comparing the diffraction amount of the optical signal received through the second step with a reference value; And a fourth step of performing a tracking operation so that the deviation of the diffraction amount of the optical signal received through the second step is equal to the reference value.

Another aspect of the present invention for achieving the above object is an optical disc player comprising: one or more condensing optical elements in proximity to a recording medium; A photodetecting element for detecting one or more lights diffracted from the recording medium and returning; An optical storage head for recording and reading information on a recording medium configured in such a manner as to obtain a tracking signal by electrical signal processing; And control means for generating a tracking control signal based on the diffraction degree of the change in the optical signal detected through the light detection element.

An additional feature of the present invention for achieving the above object is that the light transmitted through one or more condensing optical elements in proximity to the recording medium is diffracted than incident light when diffracted by the pit of the recording medium on which the information is recorded. The numerical aperture of the light is higher.

An additional feature of the present invention for achieving the above object is the use of a solid immersion lens (SIL) as a condensing optical element in proximity to a recording medium, which is diffracted with light that is internally reflected in a high refractive index lens by incident light. It is to use the light intensity distribution which the returned light interferes with each other as a tracking signal.

An additional feature of the present invention for achieving the above object is that the position of the optical detection device for detecting the diffracted light is located between the condensing optical element and the objective lens in proximity to the recording medium, and the diffracted light The position of the photodetector to detect is located on the parallel optical path.

An additional feature of the present invention for achieving the above object is that the position of the photodetector for detecting the light to be diffracted is located on the converging light path, and at least two photodetectors for detecting the light to be diffracted are Symmetrical to each other.

A further feature of the present invention for achieving the above object is that a light detecting device for detecting diffracted light is located in an optical head in the form of a flying head, and uses a semiconductor process as a light detecting device for detecting diffracted light. To use an integrated device.

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the invention described below with reference to the accompanying drawings by those skilled in the art.

First, a brief description of the technical idea to be applied in the present invention, focusing on the bottom surface of a hemispherical SIL generally made of a material having a high refractive index to track the information conventionally used in optical storage devices for recording information in a near medium The method uses a scanning scan type, which uses a micro moving mirror to find the direction of the track by vibrating the tracking light perpendicular to the track direction. However, this method has a disadvantage in that it is difficult to manufacture a micro moving mirror, consumes a lot of metal, and complicates the device.

In order to solve this problem, the present invention mounts a photodiode on a flying head and detects a tracking signal by using a phenomenon in which light focused in close proximity is diffracted by the pit and returned to a higher numerical aperture when incident. We would like to propose a tracking device.

That is, in the SIL type storage device, the numerical aperture of the light passing through is constant. This light penetrates the bottom of the SIL and becomes higher than the numerical aperture upon incidence when diffracted by the pit. If the incident light and pit do not exactly match, the distribution of light diffracted around the pit will be asymmetric. Signal processing of this asymmetry yields positive and negative values, and it is noted that the signal indicates how far the pit is out of the traveling direction.

Accordingly, the present invention proposes a method and apparatus for performing tracking using such a diffraction numerical aperture conversion method. The high density proximity tracking device proposed in the present invention is located at the end of the suspension 102 as shown in FIG. It consists of the flying head 107 and the structure as shown in FIG.

FIG. 2 shows a schematic diagram of a near field optical storage device in which a flying head 107 at the end of the suspension 102 near the disk recording medium 101, such as a hard disk, is flying at a constant height to record and reproduce information. The process of recording and reproducing information passes from the light source 104 via the optical splitter 105 to the light probe 107 through the optical waveguide 106 along the suspension 102.

The reflected light is detected by the built-in photodiode and proceeds to the signal processor 108 to detect the signal. The connection of information is carried out with the suspension 102 rotating about the axis of rotation 103.

In the tracking device proposed in the present invention, the photo detector is embedded in the flying head 107 to transmit the tracking signal along the signal line 106 connected along the suspension 102.

3 is a structure of a tracking device installed in the flying head 107 at the end of the suspension 102 in the proximity optical storage device, in which signals 204a and 204b diffracted by the pit 213 are photodiodes 206a and 206b. It is detected by, and represents the process of signal processing. The incident light 201 is focused in the SIL 203 by the objective lens 202, and the light produces light transmitted through the light according to the numerical aperture of the incident light 201 and totally internally reflected light. The transmitted light is diffracted by the pit 213 and returned to the inside of the SIL. The diffracted light at this time has a numerical aperture larger than that at the time of incidence.

This light is incident on the photodiodes 206a and 206b provided at appropriate positions by the objective lens 202. Light incident by the photodiode is converted into an electrical signal and signal processed by the adder 208, the subtractor 209, and the divider 210 to generate a tracking signal. When the incident light 201 is incident symmetrically with respect to the size of the pit 213, the diffracted light 205a, 205b is symmetrically diffracted and the intensity of light detected by the photodiodes 206a, 206b is the same.

However, if the pit 213 is asymmetrical with respect to the incident light 201, the intensity of the light 205a, 205b diffracted on both sides will also be asymmetrical. By detecting and comparing these signals, you can see how far the pit is from the travel direction.

4 of the accompanying drawings shows the shape of the tracking signal detected by the signal processing of FIG. 3, the shape of the signal is shown in the form of a push-pull method used in the conventional optical storage device, the horizontal axis is the distance axis 301 And the vertical axis is the tracking signal axis 302.

That is, in the accompanying FIG. 3, the signal moves the flying head 107 to the other direction with respect to the arrangement direction of the pit 402 according to the positive and negative in the reference direction.

5A-5C show the shape when the focal point 401 is out of the center of the pit 402, and FIG. 5A shows when the centerline 403 of the pit exactly coincides with the centerline 404 of the focal point. . The tracking signal 303 detected at this time has a value of 0 on the vertical axis in FIG. 4.

5B and 5C show when the center line 403 of the pit has moved a distance d by a distance with respect to the center line 404 of the focal point. The value at this time becomes the positive value 304 or the negative value 305 in FIG.

6 shows the principle that the light 501 for tracking interacts with the pit 402 to diffract, and includes zero-order light that returns to the center when the incident light 502 is reflected by the pit 402. It becomes + 1st order 504a and 1st order 504b which are diffracted to both sides. The intensity of the diffracted light of the + 1st order 504a and the 1st order 504b changes according to the position of both steps of the pit 402.

FIG. 7 shows the difference between the amount of light diffracted when the center line 602 of the tracking light 601 and the center of the pit 606 are shifted, and the phenomenon when the center of the pit 606 is changed by the distance d is illustrated. Indicates. When the centerline 602 of the tracking light 601 exactly coincides with the centerline of the pit 606, the intensities of the diffracted light 603a and the diffracted light 603b are the same. However, when the center line 602 of the tracking light and the center line of the pit do not coincide, the diffraction light 604b on the right is stronger or the diffraction light 605a on the left is stronger.

This diffracted light is processed by the attached signal processors of FIG. 3 to become a tracking feedback signal.

While the invention has been shown and described in connection with specific embodiments thereof, it will be appreciated that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the claims. Anyone who owns it can easily find out.

According to the present invention, there is provided a tracking method for high-density proximity optical storage and an apparatus according to the present invention operating as described above. The present invention provides a tracking signal using a diffraction light detection method in an optical information storage device of a proximity method using SIL. As a device for obtaining, the structure is simpler than the conventional scanning scan type, which is a near-field tracking method, and has a high hardware compatibility since the push-pull method used in the conventional optical storage device can be applied.

Claims (11)

In the tracking method in an optical disc player, A first step of condensing and irradiating an optical signal on the optical record carrier; A second step of receiving an optical signal reflecting and diffracted by the optical signal irradiated through the first process on the surface of the recording medium; A third step of comparing the diffraction amount of the optical signal received through the second step with a reference value; And And a fourth process of performing a tracking operation so that the deviation of the diffraction amount of the optical signal received through the second process becomes equal to a reference value. In the optical disc player, One or more condensing optical elements in proximity to the recording medium; A photodetecting element for detecting one or more lights diffracted from the recording medium and returning; An optical storage head for recording and reading information on a recording medium configured in such a manner as to obtain a tracking signal by electrical signal processing; And And a control means for generating a tracking control signal based on a diffraction degree of the change of the optical signal detected by the light detection element. The method of claim 2, When the light passing through one or more condensing optical elements in proximity to the recording medium is diffracted by the pit of the recording medium on which the information is recorded, the numerical aperture of the diffracted light becomes higher than the incident light, so that Tracking device for. The method of claim 3, wherein A tracking device for high density near-field optical storage, characterized by using a solid immersion lens (SIL) as the condensing optical element in proximity to the recording medium. The method of claim 3, wherein A tracking device for high-density near-field storage, characterized by using as a tracking signal a light intensity distribution in which light internally reflected in a high refractive index lens and incident light diffracted by incident light interfere with each other. The method of claim 2, A tracking device for high density near-field optical storage, characterized in that the position of the optical detection device for detecting the diffracted light is located between the condensing optical element and the objective lens in proximity to the recording medium. The method of claim 2, A tracking device for high density near-field light storage, characterized in that the position of the light detection device for detecting the diffracted light is located on a parallel light path. The method of claim 2, A tracking device for high density near-field light storage, characterized in that the position of the light detection device for detecting the diffracted light is located on the converging light path. The method of claim 2, 2. A tracking device for high density near-field light storage, characterized in that two or more light detection devices for detecting diffracted light are located symmetrically with each other. The method of claim 2, A tracking device for high density near-field light storage, characterized in that an optical detector for detecting diffracted light is located within an optical head in the form of a flying head. The method of claim 2, A tracking device for high-density proximity light storage, comprising: an element integrated using a semiconductor process as an optical detection device for detecting diffracted light.