JP2001184661A - Method and device for reproducing information from optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for reproducing information capable of nearly uniformizing the influence from heating caused by heat from the near-field light emitting part of a near-field light generating device even in any position of the surface of an optical recording medium when information is reproduced and facilitating a heat countermeasure for preventing the bad influence from heat caused by the near-field light generating device. SOLUTION: The information reproducing device, which reproduces information from the optical recording medium 5 whose surface 5a is moved relatively to the device 100 by using near-field light L generated from the near-field light generating device 100, is provided with an optical recording medium storing part 10, a driving device 6 for moving the surface 5a of the optical recording medium 5 stored in the storing part 10, a speed control part CONT for controlling a moving speed of the surface 5a. When information is reproduced, the relative moving speed of the part facing the near-field light generating device 100 of the surface 5a of the optical recording medium moved by the driving device 6 is nearly set to a constant relative to the device 100 by the speed control part CONT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an information reproducing method and apparatus for reproducing information from an optical recording medium using near-field light generated by a near-field light generating device.

[0002]

2. Description of the Related Art In order to record information on a recording medium and to reproduce (read) information recorded on the recording medium,
Further, in an information rewritable recording medium, near-field light may be used to erase recorded information. In recording, reproducing, and erasing information using near-field light, an optical recording medium is used as a recording medium, and information is recorded on the medium by irradiating the optical recording medium with near-field light, and information is reproduced from the medium. (Read) or erase the information on the medium.

[0003] Recording, reproducing and erasing of information using near-field light uses near-field light which is not restricted by the "light diffraction limit", so that recording, reproducing and erasing of information is performed in units smaller than the wavelength of light. It is noted that it can be performed. For example, Applied Physics Letters: 61,142,1992
(Published by the American Institute of Physics) describes recording information on a magneto-optical recording medium using near-field light. Also, US Pat. No. 5,288,998 describes a photoresist process using near-field light.

An optical recording medium used for recording information by near-field light or the like includes a heat mode recording medium for recording information using heat generated by irradiation of near-field light, and a photo-mode recording medium using near-field light photons. There is a photon mode recording medium for recording information. Examples of the former heat mode recording medium include a dye medium, a phase change recording medium, and a magneto-optical recording medium, and examples of the latter photon mode recording medium include a photochromic medium utilizing a photoreversible reaction of a photochromic material.

As a near-field light generating device used for generating near-field light, a device using a minute aperture, particularly a device in which the tip of an optical fiber is sharpened (fiber probe)
Is often used. The portion whose tip is sharpened, that is, the near-field light emitting portion from which near-field light is emitted, becomes extremely high at several hundred degrees Celsius or more due to generation of near-field light. Further, since the near-field light is generated only in the vicinity of the near-field light emitting unit,
When recording or reproducing information using near-field light, it is necessary to control the near-field light emitting unit so as to maintain a distance of several tens of nm from the optical recording medium. For this reason, there is an influence of heat propagation from the near-field light emitting portion to the optical recording medium.

[0006] Japanese Journal of Applied Physics: 7
9,8082,1996 (published by European Journal of Applied Physics), Japanes
e Journal of Applied Physics: 35, L584, 1996 describes recording information on a phase-change recording medium using a fiber probe as a near-field light generator. Among these, heat propagation to the recording medium by recording information on the phase change recording medium is caused not only by the heat generated by near-field light irradiation but also by the heat of the very high temperature of the fiber probe tip. It is stated that the effect of heating is also large.

[0007] Such a phenomenon is not limited to the fiber probe, and other near-field light generating devices, for example, a near-field light generating device in which a minute aperture is disposed at a spot position focused by a lens or the like, a minute projection, a minute projection, or the like. It also occurs in a near-field light generator that illuminates a sphere. That is, the near-field light emitting portion of the near-field light generating device using these minute openings, minute protrusions, and minute spheres becomes extremely hot and needs to be close to the recording medium. There is an effect of heat propagation from the field light emitting portion to the recording medium.

For example, when a heat mode recording medium for recording information using heat generated by irradiation of near-field light is used as an optical recording medium, erroneous recording of information or loss of a recorded state may occur. In addition, when a photon mode recording medium that records information using photons of near-field light is used, phenomena such as evaporation of the information recording layer and decomposition of a material contained in the information recording layer occur, thereby causing a photoreversible reaction. An irreversible change occurs in the material that has occurred and other materials that constitute the recording layer, and in this case, there is a possibility that information is erroneously recorded. Note that this irreversible change
In addition to irreversible changes due to irreversible reactions (decomposition, reactions other than photochromic reactions) of the photochromic material, for example, when the recording layer contains a binder resin, irreversible changes such as thermal deformation of the resin, and when it contains additives Irreversible changes due to the irreversible reaction of the additive. If these irreversible changes do not affect the reproduced signal at the time of reproducing the information at all, it does not matter, but in many cases, it does, and impairs the ON / OFF determination from the reproduced signal.

Therefore, an optical recording medium on which information is reproduced by near-field light is required to be designed so that the optical recording medium is not affected by heat propagation from the near-field light generating device. .

[0010]

The recording, reproduction and erasing of information using near-field light are usually performed on an optical recording medium whose surface moves relatively to the near-field light generating device. This is performed by irradiating near-field light generated from the light generating device. For example, when a disk-shaped optical recording medium is employed and information is reproduced from a rotating optical recording medium using near-field light generated by a near-field light generating device, the optical recording medium is subjected to a constant angular velocity condition. , The linear velocity differs depending on the radial position of the optical recording medium. That is, in the radial direction of the optical recording medium, the linear velocity decreases as the position approaches the rotation center of the medium, and increases as the distance from the rotation center of the medium increases.

For this reason, the influence of heat received from the near-field light generating device of the optical recording medium also differs. That is, the influence of the heat propagation from the near-field light generator becomes more susceptible as the near-field light generator approaches the rotation center position of the optical recording medium,
As the distance from the rotation center position of the optical recording medium increases, it becomes harder to receive. If the influence of the heat received from the near-field light generating device of the optical recording medium differs depending on the position of the medium surface, the design of the optical recording medium to cope with the situation becomes complicated.

Therefore, the present invention provides an information reproducing apparatus for reproducing information from an optical recording medium whose surface moves relatively to the near-field light generating device, using near-field light generated from the near-field light generating device. A method and an apparatus, wherein when reproducing information from an optical recording medium, the effect of heating by the heat of the near-field light emitting unit of the near-field light generating device is substantially uniform at any position on the surface of the optical recording medium. It is therefore an object of the present invention to provide a method and an apparatus for reproducing information from an optical recording medium, which make it easy to take countermeasures against heat for preventing an adverse effect of heat by the near-field light generating device on the optical recording medium.

[0013]

In order to solve the above-mentioned problems, the present invention provides the following method and apparatus for reproducing information from an optical recording medium. (1) Method of Reproducing Information from Optical Recording Medium Information is reproduced from an optical recording medium whose surface moves relatively to the near-field light generator using near-field light generated from the near-field light generator. A method for reproducing information from an optical recording medium, wherein a relative movement speed of a portion of the surface of the optical recording medium facing the near-field light generating device with respect to the device is substantially constant. A method for reproducing information from a recording medium. (2) Apparatus for reproducing information from an optical recording medium The apparatus has a near-field light generator, and the surface is relatively positioned with respect to the near-field light generator using near-field light generated from the near-field light generator. An information reproducing apparatus for reproducing information from a moving optical recording medium, comprising: an accommodation section for an optical recording medium; a driving device for moving a surface of the optical recording medium accommodated in the accommodation section; A speed control unit that controls a moving speed of the surface of the optical recording medium, wherein the speed control unit reproduces information from the optical recording medium. An apparatus for reproducing information from an optical recording medium, wherein a relative movement speed of a portion facing the near-field light generating device with respect to the near-field light generating device is substantially constant. In the method of reproducing information from an optical recording medium according to the present invention, in reproducing information from the optical recording medium, a near-field light emitting unit of the near-field light generating device is disposed in proximity to the optical recording medium, The surface is moved relative to the near-field light generator. At this time, the relative movement speed of the portion of the surface of the optical recording medium facing the near-field light generating device is substantially constant. Then, near-field light is generated from a near-field light emitting unit of the near-field light generating device, and the optical recording medium is irradiated with the near-field light to reproduce information from the optical recording medium.

An information reproducing apparatus for reproducing information from an optical recording medium according to the present invention includes a near-field light generating device, and includes a housing for the optical recording medium and a drive for moving the surface of the optical recording medium housed in the housing. A device for controlling the moving speed of the surface of the optical recording medium moved by the driving device. In the information reproducing apparatus, when reproducing information from an optical recording medium, a near-field light emitting unit of the near-field light generating device is disposed in proximity to the optical recording medium, and the surface of the optical recording medium is moved in close proximity by the driving device. It is moved relatively to the field light generator. At this time, the speed control unit makes the relative moving speed of the portion of the surface of the optical recording medium, which is moved by the driving device, facing the near-field light generator relatively constant with respect to the near-field light generator. Then, near-field light is generated from a near-field light emitting unit of the near-field light generating device, and the optical recording medium is irradiated with the near-field light to reproduce information from the optical recording medium.

According to the method and apparatus for reproducing information from an optical recording medium according to the present invention, when reproducing information from an optical recording medium, the near-field light generator generates near-field light from a near-field light emitting unit. Although the near-field light emitting portion is at a high temperature, the relative movement speed of the surface portion of the optical recording medium with respect to the near-field light generating device is made substantially constant, so that the near-field light is emitted at any position on the optical recording medium surface. The effect of heating by the heat of the near-field light emitting portion of the light generating device can be made substantially uniform. This facilitates measures for preventing the adverse effect of heat by the near-field light generator on the optical recording medium.

The optical recording medium which can be used in the method and apparatus for reproducing information from the optical recording medium of the present invention includes a heat mode recording medium for recording information using heat generated by irradiation of near-field light, A photon mode recording medium that records information using photons of field light can be exemplified.
Examples of the heat mode recording medium include a dye medium, a phase change recording medium, and a magneto-optical recording medium, and examples of the photon mode recording medium include a photochromic medium using a photoreversible reaction of a photochromic material. it can.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a schematic configuration of a part of an example of an information reproducing apparatus for executing a method for reproducing information from an optical recording medium according to the present invention. The information reproducing device shown in FIG. 1 includes a near-field light generating device 100, a reproduced information detecting device 20.
0, optical recording medium storage unit 10, radial driving device 11,
A light that includes the rotation driving device 6 and the speed control unit CONT, and that uses the near-field light L generated from the near-field light generation device 100 to move the surface 5a relatively to the near-field light generation device 100 The information is reproduced from the recording medium 5. That is, when reproducing information from the optical recording medium 5 stored in the storage unit 10, the optical recording medium 5 that is rotationally driven by the rotation driving device 6 under the instruction of the speed control unit CONT.
The near-field light L is applied to the surface 5a of the medium 5 from the near-field light generator 100, the amount of the reflected light 7 reflected on the surface 5a of the medium 5 is detected by the reproduction information detection device 200, and the reading (reproduction) of information is performed. Do.

The near-field light generating device 100 includes a laser light source 1, an optical coupling device 3, and a near-field light emitting unit 4. The laser light source 1 is a laser light 2 (here, a wavelength 51).
4 nm of visible light) can be emitted toward the optical coupling device 3. The optical coupling device 3 can focus the laser light 2 from the laser light source 1 on the near-field light emitting unit 4. Near-field light emitting unit 4
Can convert the laser light 2 from the optical coupling device 3 into near-field light L.

The radial driving device 11 causes the near-field light generator 100 to move the near-field light generating device 100 along the surface 5 a of the optical recording medium 5.
In the radial direction (X direction in the figure).
In addition, the driving device 11 is connected to the speed control unit CONT, and can send position information of the near-field light generating device 100 in the radial direction X to the speed control unit CONT. The storage section 10 for an optical recording medium can accommodate a disk-shaped (disk-shaped) optical recording medium 5.

As the optical recording medium 5, a photochromic medium as a photon mode recording medium or a dye medium as a heat mode recording medium can be employed. FIG. 3 shows an optical recording medium 5.
FIG. 4 is a schematic cross-sectional view of a part of a photochromic medium adopted as the optical recording medium, and FIG.

The photochromic medium 5 shown in FIG. 3 comprises a photochromic material and a polymethyl methacrylate resin (weight ratio of photochromic material to polymethyl methacrylate resin 1: 1) on a glass substrate 51A having a diameter of 12 cm.
The information recording layer 52A is formed by spin coating. The thickness of the information recording layer 52A is about 150 nm here. FIG. 5 shows the chemical structural formula of the photochromic material used for the photochromic medium 5.

This photochromic material has a wavelength of 308
Irradiation of ultraviolet light of nm causes a reversible change from the structure on the left side in FIG. 5 to the structure on the right side in FIG. 5, and irradiation of visible light having a wavelength of 514 nm causes a reversible change from the structure on the right side to the structure on the left side. Here, the photochromic medium 5 can be used as an information rewritable optical recording medium by associating the state of the structure on the right side of the photochromic material with an unrecorded state and the state of the structure on the left side with the information recorded state. Reproduction of information from the photochromic medium 5 is performed at a wavelength of 514 nm.
m when the photochromic medium 5 is irradiated with light of m.
This is done by monitoring the intensity of the reflected light from the light source. The melting point of the photochromic material used for the photochromic medium 5 is about 70 ° C., and the glass transition point of the polymethyl methacrylate resin is also about 70 ° C.

The dye medium 5 shown in FIG. 4 is obtained by forming an information recording layer 52B made of a cyanine dye and a polymethyl methacrylate resin on a glass substrate 51B having a diameter of 5 cm by a spin coating method. The layer thickness of the information recording layer 52B is
Here, it is about 90 nm. FIG. 6 shows the chemical structural formula of the cyanine dye used in the dye medium 5. The cyanine dye generates heat by irradiation with visible light having a wavelength of 514 nm.
In the dye medium 5, heat of the cyanine dye caused by irradiation of visible light with a wavelength of 514 nm causes thermal deformation of the surrounding polymethyl methacrylate resin, whereby information can be recorded. Reproduction of information from the dye medium 5 is performed at a wavelength of 514 n.
This is performed by monitoring the intensity of the reflected light from the medium 5 when the dye medium 5 is irradiated with the light of m. The cyanine dye has no melting point or decomposition point up to about 250 ° C.
The glass transition point of the polymethyl methacrylate resin is about 70 ° C.

The rotary drive device 6 shown in FIG. 1 is arranged at the center of the housing 10 and includes a rotary mechanism 6a.
The rotation mechanism 6a is connected to the speed control unit CONT,
The rotation center portion of the optical recording medium 5 housed in the housing section 10 can be fixed. Thus, the rotation driving device 6 can rotationally drive the optical recording medium 5 by the rotation mechanism 6a under the instruction of the speed control unit CONT. That is, the medium surface 5a is moved to the near-field light generating device 100 (more precisely, the near-field light emitting unit 4).
Can be relatively moved with respect to.

Here, for example, when the speed control unit CONT rotates the optical recording medium 5 under the constant angular velocity condition, the linear velocity differs depending on the position of the optical recording medium 5 in the radial direction X. In other words, the linear velocity in the radial direction X of the optical recording medium 5 decreases as the position approaches the rotation center position of the medium 5 and increases as the distance from the rotation center position of the medium increases. However, the speed control unit CONT here is connected to the radial driving device 11 and based on the position information in the radial direction X of the near-field light generating device 100 sent from the driving device 11, the optical recording medium 5. So that the linear velocity becomes substantially constant at any position in the radial direction X of the medium 10, that is, the portion of the device 10 of the portion of the medium surface 5 a facing the near-field light emitting section 4 of the near-field light generating device 100.
The rotation driving device 6 is controlled such that the relative movement speed with respect to the near-field light emitting unit 4 becomes substantially constant.

FIG. 2 is a more detailed side view of the near-field light emitting section 4 shown in FIG. The near-field light emitting section 4 includes an optical recording medium 5
A small opening 4b is provided in a head 4a which floats by a floating force caused by an air flow generated by the rotation of. The head 4a has an opening entrance 4c (opening diameter 600 nm in this example) on the wide side of the minute opening 4b and an opening exit 4d (opening diameter 200 nm in this example) on the narrow side of the minute opening 4b. Thereby, the near-field light emitting section 4 can emit the near-field light L from the opening exit 4d by the laser light 2 from the optical coupling device 3 being incident on the opening entrance 4c.

In the information reproducing apparatus shown in FIG. 1, the distance between the near-field light emitting unit 4 and the medium 5 is not detected, and the medium surface 5a is moved by the rotary driving device 6, and the near-field light emitting The distance between the near-field light emitting unit 4 and the medium surface 5a is controlled by the levitation force of the near-field light emitting unit 4 due to the air flow generated between the unit 4 and the medium surface 5a. The reproduction information detection device 200
It includes a condenser lens 8 and a photodiode 9. The condenser lens 8 irradiates the medium 5 with light from the near-field light emitting unit 4 so that the reflected light 7 reflected on the medium surface 5a can be collected on the photodiode 9. The photodiode 9 can photoelectrically convert the light collected by the condenser lens 8 according to the light intensity. This signal is detected as a light amount by the electric circuit 9 '.

The information reproducing apparatus has a main control unit (not shown). The main control section is mainly composed of a computer and controls the entire information reproducing apparatus.
That is, it is connected to the laser light source 1, the radial driving device 11, the reproduction information detecting device 200, and controls the emission timing of the laser light 2 by the laser light source 1 and generates the near-field light by the radial driving device 11. The position of the apparatus 100 in the radial direction X is controlled, or information is read from the medium 5 based on the detection result of the reproduction information detection apparatus 200.

According to the information reproducing apparatus described above, when reproducing information from the optical recording medium 5, the driving device 6
Accordingly, the medium 5 is driven to rotate. That is, the surface 5a of the optical recording medium 5 is relatively moved with respect to the near-field light emitting unit 4 of the near-field light generating device 100. At this time, the relative movement speed of the portion of the moving medium surface 5a facing the near-field light generating device 100 with respect to the device 100 is made substantially constant by the driving device 6 based on an instruction from the speed control unit CONT. The near-field light emitting unit 4 floats by a levitation force due to the airflow generated by the rotation of the medium 5, and the distance between the near-field light emitting unit 4 and the medium surface 5a is controlled.

Next, laser light 2 is emitted from the laser light source 1. Laser light 2 emitted from laser light source 1
Is incident on the near-field light emitting unit 4 via the optical coupling device 3,
Here, it is converted into near-field light L. Converted near-field light L
Are emitted from the exit 4d of the near-field light emitting unit 4 and irradiate the surface 5a of the disc-shaped optical recording medium 5. At this time, in the near-field light generating device 100, the near-field light emitting unit 4 is at a high temperature due to the generation of the near-field light L from the near-field light emitting unit 4.

The near-field light L emitted from the opening exit 4d of the near-field light emitting section 4 and irradiating the optical recording medium surface 5a is reflected by the medium 5. The reflected light 7 is collected by a condenser lens 8, then photoelectrically converted by a photodiode 9, and the amount of light is detected by an electric circuit 9 '. According to the information reproducing apparatus for performing the information reproducing method from the optical recording medium according to the present invention shown in FIG. 1, the near-field light emitting unit 4 is at a high temperature when reproducing information from the optical recording medium 5, Near-field light generating device 10 on surface 5a of optical recording medium 5
Since the relative movement speed with respect to 0 is made substantially constant, the influence of heating by the heat of the near-field light emitting unit 4 of the near-field light generating device 100 can be made substantially uniform at any position in the radial direction X of the medium surface 5a. Thereby, the adverse effect of heat by the near-field light generating device 100 on the optical recording medium 5, for example, erroneous recording of information, in other words, the portion of the medium 5 where the information is not recorded is the near-field light emitting section 4 where the temperature has become high. Heat is propagated due to the propagation of the heat, an irreversible change occurs, and as a result, when reproducing information, a reproduction signal is given as if it were in an information recording state. This makes it easy to take countermeasures (for example, speed adjustment for that) in order to prevent the recording state.

The information reproducing apparatus described in this embodiment employs a flying head type near-field light generating device in which a minute aperture is provided at a spot position converged by the optical coupling device 3 as the near-field light generating device 100. However, the present invention is not limited to this. A near-field light generating device of a fiber probe type having a minute aperture, a near-field light generating device for illuminating a microprojection or a microsphere, or a near field using a SIL (Solid Immersion Lens) A light generating device or the like may be employed.

Next, an information reproduction experiment was performed, and the experiment will be described below. In the experiment, the optical recording medium 5 was accommodated in the information reproducing apparatus shown in FIG. 1, and the above-described control (that is, the optical recording medium 5 was driven under a substantially constant linear velocity condition) was performed as rotation control for the rotation drive device 6 of the speed control unit CONT. In addition to the control for rotating the optical recording medium, a control for rotating the optical recording medium 5 under a substantially constant angular velocity condition was added as a comparative experiment.

As the optical recording medium 5, two types of a photochromic medium shown in FIG. 3 and a dye medium shown in FIG.
Optical recording media A and B were used, respectively. Note that the optical recording media A and B used in the experiment have previously recorded patterns as shown in FIG. 7 as recording information. In the figure, R
Is an information recording section, and the information recording section R is recorded at a center angle of 5 degrees (α in the figure) about the center of rotation of the optical recording medium 5 with a width of 900 nm (d in the figure).

In this information reproducing experiment, in the information reproducing apparatus shown in FIG. 1, the position of the near-field light emitting section 4 of the near-field light generating apparatus 100 in the radial direction X of the optical recording media A and B (medium rotation center position is 0) and the rotational speeds of the optical recording media A and B as parameters. That is, the optical recording media A and B are rotated under substantially constant linear velocity conditions or substantially constant angular velocities, respectively, in the radial direction X of the media A and B from the media rotation center position by 1 cm, 1.5 cm, 2 cm,
The reproduction state of the information recording pattern at a position of 2.5 cm was examined.

Table 1 shows the experimental results. In the table, “○” means that the information recording pattern was successfully reproduced, and “×” means that the information recording pattern was not successfully reproduced. The remarks also indicate the reason why the information recording pattern was not successfully reproduced.

[0037]

[Table 1]

As shown in Table 1, when the optical recording media A and B are respectively rotated at a substantially constant linear velocity, the optical recording medium A has a linear velocity of 10 cm / s and 20 cm / s, and the optical recording medium B has a linear velocity. Speed 10cm / s, 20cm / s, 50cm /
At s, information could be reproduced successfully at any position on the medium surface. This is because the medium is rotated under such a condition that the linear velocity is substantially constant in reproducing the information. In other words, the relative movement speed of the portion of the medium surface facing the near-field light generating device 100 with respect to the device 100 is substantially constant. Near field light generator 100 at any position on the medium surface
It is considered that the influence of the heating by the heat of the near-field light emitting unit 4 became substantially uniform within the allowable range. In the optical recording media A and B, the linear velocity was 2 cm / s and the linear velocity was 5 cm.
/ S, the adverse effect of heat by the near-field light emitting unit 4, that is, erroneous recording of information, in other words, the portions of the mediums A and B in the information unrecorded state become the near-field light generating device 100 in which the temperature becomes high. A phenomenon in which the heat of the near-field light emitting portion 4 is heated by the propagation of the heat and causes an irreversible change, and as a result, a reproduced signal as if in an information recording state is given at the time of reproducing information (of course, information (In some cases, the recording state may be as if the information has not been recorded.) However, since the influence of this heat is considered to be substantially uniform, the heat of the optical recording mediums A and B is considered. This makes it easy to take measures to prevent the adverse effects of

On the other hand, when the optical recording media A and B are respectively rotated at substantially constant angular velocities, for example, when the angular velocities are 5 rad / s, the positions close to the rotation center positions of the media A and B ( The position of the optical recording medium A is 1.5 cm or less from the rotation center position, and the position of the optical recording medium B is 1 cm from the rotation center position. This is because the optical recording media A, B
Linear velocity varies depending on the position in the radial direction X of the optical recording media A and B, that is, the linear velocity decreases in the radial direction X of the optical recording media A and B as it approaches the rotation center position of the medium, and increases as the distance from the rotation center position of the medium increases. It is considered that the influence of the heat received from the near-field light emitting portions 4 of the optical recording media A and B is different. That is, the influence of heat received from the near-field light emitting units 4 of the optical recording media A and B depends on the near-field light emitting units 4.
Is more likely to be received as the media approaches the rotation center positions of the media A and B, and becomes harder to receive as the media A and B move away from the rotation center positions.

As shown in Table 1, optical recording media A,
When B is rotated under substantially constant linear velocity conditions and when rotated under substantially constant angular velocity conditions, in any case, at relatively low speeds, erroneous recording of information due to heat propagation from the near-field light emitting unit 4 causes At a relatively high speed, the S / N ratio of the information reproduction signal is reduced, which indicates that the range in which the information recording pattern can be reproduced successfully is determined.

When the optical recording media A and B are rotated under substantially constant linear velocity conditions, the optical recording medium A has a linear velocity of 10 c.
When the linear velocity is 10 cm / s to 50 cm / s, information can be reproduced successfully at any position on the optical recording medium B at m / s to 20 cm / s. The allowable range of the speed is 10 cm / s to 20 cm / s for the optical recording medium A and 10 cm / s to 50 cm / s for the optical recording medium B. On the other hand, when the optical recording media A and B are respectively rotated under substantially constant angular velocity conditions, the optical recording medium A has an angular velocity of 5 degrees.
rad / s and 20 rad / s, the optical recording medium B
In the optical recording media A and B at angular velocities of 5 rad / s and 50 rad / s, there are a position where information can be reproduced successfully and a position where information cannot be reproduced properly. The recording medium A has an angular velocity of 10 rad / s, and the optical recording medium B has an angular velocity of 10 rad / s to 20 rad / s, which is smaller than the allowable range when the optical recording mediums A and B are rotated at substantially constant linear velocities.

[0042]

As described above, according to the present invention, the near-field light generated from the near-field light generating device is used to move the optical recording medium whose surface moves relatively to the near-field light generating device. An information reproducing method and apparatus for reproducing information, wherein when reproducing information from an optical recording medium, at any position on the surface of the optical recording medium, heat is generated by a near-field light emitting unit of a near-field light generating device. It is possible to provide a method and an apparatus for reproducing information from an optical recording medium, in which the influence of heating can be made substantially uniform, thereby facilitating measures against heat for preventing adverse effects of heat by the near-field light generator of the optical recording medium. .

[Brief description of the drawings]

FIG. 1 is a side view showing a schematic configuration of a part of an example of an information reproducing apparatus for executing a method of reproducing information from an optical recording medium according to the present invention.

FIG. 2 is a more detailed side view of the near-field light emitting unit shown in FIG.

FIG. 3 is a schematic sectional view of a part of a photochromic medium.

FIG. 4 is a schematic sectional view of a part of a dye medium.

FIG. 5 shows a chemical structural formula of a photochromic material.

FIG. 6 shows a chemical structural formula of a cyanine dye.

FIG. 7 is a plan view of a part of an optical recording medium used in an information reproducing experiment, showing an information recording pattern recorded on the medium.

[Explanation of symbols]

 Reference Signs List 1 laser light source 2 laser light 3 optical coupling device 4 near-field light emitting part 4a head 4b minute opening 4c opening entrance 4d opening exit 5 optical recording medium 5a surface of optical recording medium 5 51A, 51B glass substrate 52A, 52B information recording layer 6 Rotation driving device 6a Rotating mechanism 7 Reflected light 8 Condensing lens 9 Photodiode 9 'Electric circuit of photodiode 9 10 Housing for optical recording medium 11 Radial driving device 100 Near-field light generation device 200 Reproduction information detection device CONT Speed control Part L Near-field light R Information recording part d Width of information recording part R

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G065 AA04 AB04 AB09 AB22 BA09 BA26 BB02 BC01 CA13 5D090 AA01 CC04 DD03 EE11 FF11 HH01 LL07 5D119 AA11 AA22 BA01 CA06 DA05 EC18

Claims (2)

[Claims] An information reproducing method for reproducing information from an optical recording medium whose surface moves relatively to the near-field light generating device using near-field light generated from the near-field light generating device. Reproducing information from an optical recording medium, wherein a relative movement speed of a portion of the surface of the optical recording medium facing the near-field light generating device with respect to the device is made substantially constant. Method. 2. An optical recording medium having a near-field light generator, wherein a surface of the optical recording medium moves relative to the near-field light generator using near-field light generated from the near-field light generator. An information reproducing apparatus that reproduces information, comprising: an accommodation section for an optical recording medium; a driving device that moves a surface of the optical recording medium accommodated in the accommodation section; and a surface of the optical recording medium that is moved by the driving device. A speed control unit for controlling a moving speed of the optical recording medium, wherein the speed control unit reproduces information from the optical recording medium, and the near-field light generating device on the surface of the optical recording medium moved by the driving device. An apparatus for reproducing information from an optical recording medium, wherein a relative movement speed of a part facing the near-field light generator is substantially constant.