Recording medium and information recording and reproducing method using the same

A recording medium, comprising:

• i) a substrate, and
• ii) a recording layer overlaid on the substrate,
• wherein the recording layer comprises multiple kinds of materials uniformly mixed together, each of which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material,
• the multiple kinds of the materials are capable of being caused by the recording light having different wavelengths λ1 to change into fluorescent materials,
• the fluorescent materials, which have been formed by the multiple kinds of the materials, are capable of being caused by excitation light having different wavelengths λ2 to produce fluorescence, and
• the fluorescent materials, which have been formed by the multiple kinds of the materials, produce the fluorescence having different wavelengths λ3.

A recording medium, comprising:

• i) a substrate, and
• ii) a recording layer overlaid on the substrate,
• wherein the recording layer comprises multiple kinds of materials uniformly mixed together, each of which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material,
• the multiple kinds of the materials are capable of being caused by the recording light having different wavelengths λ1 to change into fluorescent materials,
• the fluorescent materials, which have been formed by the multiple kinds of the materials, are capable of being caused by excitation light having an identical wavelength λ2 to produce fluorescence, and
• the fluorescent materials, which have been formed by the multiple kinds of the materials, produce the fluorescence having different wavelengths λ3.

A recording medium, comprising:

• i) a substrate, and
• ii) a recording layer overlaid on the substrate,
• wherein the recording layer comprises multiple kinds of materials uniformly mixed together, each of which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material,
• the multiple kinds of the materials are capable of being caused by the recording light having different wavelengths λ1 to change into fluorescent materials,
• the fluorescent materials, which have been formed by the multiple kinds of the materials, are capable of being caused by excitation light having different wavelengths λ2 to produce fluorescence, and
• the fluorescent materials, which have been formed by the multiple kinds of the materials, produce the fluorescence having an identical wavelength λ3.

An information reproducing method for reproducing recording information from a recording medium, on which the recording information has been recorded, wherein the recording information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light carries the recording information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the method comprising the steps of:

• i) providing the recording medium, the recording medium comprising:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence;
• ii) irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer, the fluorescent material being thereby caused to produce the fluorescence;
• and
• iii) detecting the fluorescence,
• wherein light having the wavelength λ2 different from the wavelength λ1 of the recording light is employed as the excitation light.

An information reproducing method for reproducing recording information from a recording medium, on which the recording information has been recorded, wherein the recording information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light carries the recording information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the method comprising the steps of:

• i) providing the recording medium, the recording medium comprising:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence;
• ii) irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer, the fluorescent material being thereby caused to produce the fluorescence;
• and
• iii) detecting the fluorescence,
• wherein the recording medium is constituted such that the substrate comprises a dielectric material, a metal film is overlaid on one surface of the dielectric material, and the recording layer is overlaid on the metal film, and
• wherein the excitation light is irradiated from the substrate side to the recording medium such that the excitation light impinges at a specific angle of incidence upon the metal film.

An information reproducing apparatus for reproducing recording information from a recording medium, on which the recording information has been recorded, wherein the recording information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light carries the recording information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the apparatus comprising:

• i) excitation means for irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer in order to cause the fluorescent material to produce the fluorescence, and
• ii) read-out means for detecting the fluorescence,
• wherein the recording medium comprises:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence, and
• wherein the excitation means irradiates light, which has the wavelength λ2 different from the wavelength λ1 of the recording light, as the excitation light to the recording layer.

An information reproducing apparatus for reproducing recording information from a recording medium, on which the recording information has been recorded, wherein the recording information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light carries the recording information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the apparatus comprising:

• i) excitation means for irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer in order to cause the fluorescent material to produce the fluorescence, and
• ii) read-out means for detecting the fluorescence,
• wherein the recording medium comprises:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence,
• wherein the excitation means scans the recording layer with converged beam-like excitation light,
• wherein the read-out means detects the fluorescence with respect to each of positions which are being scanned with the excitation light,
• wherein the recording medium is constituted such that the substrate comprises a dielectric material, a metal film is overlaid on one surface of the dielectric material, and the recording layer is overlaid on the metal film, and
• wherein the excitation means irradiates the excitation light to the recording medium such that the excitation light impinges upon the metal film from the substrate side.

A recording medium, comprising:

• i) a substrate, and
• ii) a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence having an intensity in accordance with the intensity of the recording light, and
• wherein the wavelength λ1 of the recording light and the wavelength λ2 of the excitation light are different from each other.

A recording medium, comprising:

• i) a substrate, and
• ii) a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence having an intensity in accordance with the intensity of the recording light, and
• wherein the substrate comprises a dielectric material, a metal film is overlaid on one surface of the dielectric material, and the recording layer is overlaid on the metal film.

A recording medium, comprising:

• i) a substrate, and
• ii) a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence having an intensity in accordance with the intensity of the recording light, and
• wherein the substrate comprises a material permeable to the excitation light having the wavelength λ2.

A multi-valued information reproducing method for reproducing multi-valued information from a recording medium, on which the multi-valued information has been recorded, wherein the multi-valued information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light has an intensity in accordance with the multi-valued information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the method comprising the steps of:

• i) providing the recording medium, the recording medium comprising:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence having an intensity in accordance with the intensity of the recording light;
• ii) irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer, the fluorescent material being thereby caused to produce the fluorescence having an intensity in accordance with the intensity of the recording light;
• and
• iii) detecting the fluorescence,
• wherein light having the wavelength λ2 different from the wavelength λ1 of the recording light is employed as the excitation light.

A multi-valued information reproducing method for reproducing multi-valued information from a recording medium, on which the multi-valued information has been recorded, wherein the multi-valued information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light has an intensity in accordance with the multi-valued information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the method comprising the steps of:

• i) providing the recording medium, the recording medium comprising:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence having an intensity in accordance with the intensity of the recording light;
• ii) irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer, the fluorescent material being thereby caused to produce the fluorescence having an intensity in accordance with the intensity of the recording light;
• and
• iii) detecting the fluorescence,
• wherein the recording medium is constituted such that the substrate comprises a dielectric material, a metal film is overlaid on one surface of the dielectric material, and the recording layer is overlaid on the metal film, and
• wherein the excitation light is irradiated from the substrate side to the recording medium such that the excitation light impinges at a specific angle of incidence upon the metal film.

A multi-valued information reproducing apparatus for reproducing multi-valued information from a recording medium, on which the multi-valued information has been recorded, wherein the multi-valued information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light has an intensity in accordance with the multi-valued information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the apparatus comprising:

• i) excitation means for irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer in order to cause the fluorescent material to produce the fluorescence having an intensity in accordance with the intensity of the recording light;
• and
• ii) read-out means for detecting the fluorescence,
• wherein the recording medium comprises:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence having an intensity in accordance with the intensity of the recording light, and
• wherein the excitation means irradiates light, which has the wavelength λ2 different from the wavelength λ1 of the recording light, as the excitation light to the recording layer.

A multi-valued information reproducing apparatus for reproducing multi-valued information from a recording medium, on which the multi-valued information has been recorded, wherein the multi-valued information has been recorded on the recording medium by irradiating the recording light having the predetermined wavelength λ1, which recording light has an intensity in accordance with the multi-valued information, to the recording layer of the recording medium, the material, which is located at a site having been exposed to the recording light, being thereby caused to change into the fluorescent material, the apparatus comprising:

• i) excitation means for irradiating the excitation light having the wavelength λ2, which falls within an excitation wavelength region for the fluorescent material, to the recording layer in order to cause the fluorescent material to produce the fluorescence having an intensity in accordance with the intensity of the recording light;
• and
• ii) read-out means for detecting the fluorescence,
• wherein the recording medium comprises:
• a substrate, and
• a recording layer overlaid on the substrate,
• wherein the recording layer comprises a material, which has properties such that, when recording light having a predetermined wavelength λ1 is irradiated to the material, the material is capable of being caused to change into a fluorescent material and such that, when excitation light having a wavelength λ2 is then irradiated to the thus formed fluorescent material, the fluorescent material is capable of being caused to produce fluorescence having an intensity in accordance with the intensity of the recording light,
• wherein the excitation means scans the recording layer with converged beam-like excitation light,
• wherein the read-out means detects the fluorescence with respect to each of positions which are being scanned with the excitation light,
• wherein the recording medium is constituted such that the substrate comprises a dielectric material, a metal film is overlaid on one surface of the dielectric material, and the recording layer is overlaid on the metal film, and
• wherein the excitation means irradiates the excitation light to the recording medium such that the excitation light impinges upon the metal film from the substrate side.