JP2000099948A - Information recording, reproducing and erasing device of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording, reproducing and erasing device of an optical recording medium capable of eliminating the separate need for a light source for information reproduction only, suppressing the destruction of recorded information and reproducing the information. SOLUTION: This device includes the light source 21 which is the light source for information reproduction and information erasure and is also a light source for emitting light of a specified basic wavelength λ, a wavelength conversion device 100, a wavelength control section 200, an optical system 300 and a phodetector 40 (refractive index detector) accompanied by a pinhole member 40a. At the time of erasure, the device erases the information by irradiating the medium M with the light of the wavelength λ2 of the large absorbancy index of a photochromic material from the conversion device 100 via the optical system 300 by the control section 200. At the time of reproduction, the device irradiates the medium M with the light of the wavelength λ3 of the small absorbancy index of the photochromic material from the conversion device 100 via the optical system 300 by the control section 200 and detects and reproduces the information with the pinhole member 40a and the photodetector 40 from the difference in the reflection position of the light in the information recording state and information non-recording state thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to recording information on an optical recording medium whose information recording area is made of a photochromic material and irradiating the optical recording medium with light from the light source, and reproducing information from the optical recording medium. Alternatively, the present invention relates to an information recording / reproducing / erasing apparatus for an optical recording medium for erasing information from the optical recording medium.

[0002]

2. Description of the Related Art An information recording, reproducing and erasing apparatus generally uses a recording medium on which information can be rewritten, and records information on the recording medium, reproduces information from the recording medium, or deletes information on the recording medium. Perform erasure. As a rewritable recording medium for information, an optical recording medium utilizing a photoreaction of a photochromic material has been conventionally proposed. An information recording, reproducing, and erasing apparatus using this optical recording medium irradiates the optical recording medium with light from a light source, thereby recording information on the optical recording medium, reproducing information from the optical recording medium, or reproducing the information. The information on the optical recording medium is erased.

An optical recording medium utilizing the photoreaction of a photochromic material has two states generated by a photochromic reaction, which will be described later, in an information unrecorded state (a state in which no information is recorded) and an information recorded state (an information recorded state). (Recorded state). The photochromic reaction means that a photochromic material in the state A is irradiated with light having a wavelength λ1 in which the state A absorbs, thereby generating a state B in which light of a different wavelength is absorbed. B in the photochromic material
State is a reversible reaction that returns to the original state of A by irradiating light of wavelength λ2 having absorption.

By utilizing this reaction, such an optical recording medium can be rewritten, for example, by associating the state A and the state B of the photochromic material with the information unrecorded state and the information recorded state, respectively. In this case, the light having the wavelength λ1 is the information recording light, the light having the wavelength λ2 is the information erasing light, and the larger the absorbance of the photochromic material in the state A under the light having the wavelength λ1, the better the information recording efficiency. The greater the absorbance of the photochromic material in the state B under the wavelength of 2 light, the better the information erasing efficiency.

[0005] Further, since the light absorption spectrum before and after the photochromic reaction, that is, when the photochromic material is in the state of A and in the state of B, the absorption spectrum of light at a certain wavelength, for example, the wavelength λ2, must be detected. As a result, reading of an information recorded state or an unrecorded state, that is, reproduction of information becomes possible. The information recording / reproducing / erasing apparatus for an optical recording medium using such a photochromic material has the following problems. That is, light of two wavelengths is required for recording and erasing information, in other words, two light sources, a light source for information recording and a light source for information erasing, are required. In order to solve such a problem, for example, Japanese Patent Laid-Open No. 6-76335 discloses that a fundamental wave (wavelength λ2) of light from a light source is used as information erasing light, and the light from the light source is converted by a nonlinear optical element. An information recording / reproducing / erasing apparatus for an optical recording medium which enables recording and erasing of information with one light source by using a second harmonic (wavelength λ1) obtained as a light for recording information is taught. Also,
For example, it is described that the erasing light having the wavelength λ2 can be used for reproducing information. However, in such an apparatus, although information can be recorded and erased by one light source, when the light of wavelength λ2 is used as reproduction light and the information is reproduced by detecting the absorption intensity of the light in this reproduction light, the reproduction of wavelength λ2 is performed. Since light also acts as erasing light, the erasing reaction of the photochromic reaction (reaction returning from the state of B to the state of A) by repeated irradiation of the reproducing light progresses, and the information recording state is destroyed as the number of reproductions increases. Will be.

[0006] Regarding such a problem, Japanese Patent Laid-Open Publication No.
JP-A-39718 discloses a method of irradiating an optical recording medium with light having a wavelength at which a photochromic reaction hardly proceeds, that is, light having a long wavelength in which both the A and B states of the photochromic material hardly absorb. Has proposed a method of reproducing information by detecting a change in optical refractive index in the medium.

[0007]

However, as disclosed in Japanese Patent Application Laid-Open No. 2-139718, when information is reproduced by detecting a change in the refractive index using light of a long wavelength where the photochromic reaction hardly progresses, the recording light is increased. , The need for erasing light and reproduction light of a wavelength different from these wavelengths,
A device for recording, reproducing and erasing information on an optical recording medium further requires a light source for information recording and information erasing and a light source for information reproduction different from these light sources.

Accordingly, the present invention provides a method of recording information on an optical recording medium, reproducing information from the optical recording medium, or reproducing information from the optical recording medium by irradiating light from a light source to an optical recording medium whose information recording region is made of a photochromic material. An information recording / reproducing / erasing apparatus for an optical recording medium for erasing information on an optical recording medium, wherein information is reproduced without requiring a separate light source exclusively for information reproduction and suppressing destruction of recorded information. Information recording on an optical recording medium that can achieve the downsizing of the device and the cost reduction,
It is an object to provide a reproducing and erasing device.

[0009]

According to the present invention, there is provided the following information recording apparatus for recording information on first to third optical recording media.
Provide a reproducing and erasing device. (1) Information recording, reproducing (reading), and erasing device of the first optical recording medium The information recording area is irradiated with light from a light source to the optical recording medium made of a photochromic material to record information on the optical recording medium. Information recording on an optical recording medium for reproducing (reading) information from the optical recording medium or erasing information from the optical recording medium;
In a reproducing (reading) and erasing apparatus, a light source for emitting light of a certain fundamental wavelength, which is a light source for information reproducing (reading) and a light source for information erasing (or information recording), and a wavelength of light from the light source. A wavelength conversion device that converts the light into a predetermined wavelength, a wavelength control unit that controls the wavelength conversion of light by the wavelength conversion device, and an optical system for condensing light from the wavelength conversion device on the optical recording medium. A refractive index detecting device for detecting a refractive index of light applied to the optical recording medium, and when erasing information (or at the time of recording information), under the control of the wavelength control unit, When irradiating the optical recording medium with light having a large absorbance of the photochromic material from the wavelength conversion device through the optical system to erase information (or record information) and reproduce (read) information, And said Under the control of the length control unit, the wavelength conversion device irradiates the optical recording medium with light having a wavelength at which the absorbance of the photochromic material is small through the optical system. An information recording, reproducing (reading), and erasing device for an optical recording medium, wherein a difference in a refractive index of the light in a recording state is detected by the refractive index detecting device to reproduce (read) information. (2) Information recording, reproducing (reading), and erasing device of the second optical recording medium The information recording area is irradiated with light from a light source to the optical recording medium made of a photochromic material to record information on the optical recording medium. Information recording on an optical recording medium for reproducing (reading) information from the optical recording medium or erasing information from the optical recording medium;
In a reproducing (reading) and erasing apparatus, a light source that emits light of a certain basic wavelength, which is a light source for information reproducing (reading) and is also a light source for information erasing and information recording, and a wavelength of light from the light source are set to predetermined values. A wavelength converter that converts the wavelength, a wavelength controller that controls the wavelength conversion of light by the wavelength converter, an optical system for condensing light from the wavelength converter on the optical recording medium, and A refractive index detecting device for detecting a refractive index of light applied to the optical recording medium, and when erasing information, absorbance of the photochromic material from the wavelength conversion device under the control of the wavelength control unit. The information is erased by irradiating the optical recording medium with erasing light having a large wavelength through the optical system, and at the time of recording the information, the wavelength conversion device transmits the information under the control of the wavelength control unit. Information is recorded by irradiating the optical recording medium with the recording light having a wavelength having a large absorbance of the photochromic material via the optical system, and at the time of reproducing (reading) the information, under the control of the wavelength control unit. The wavelength conversion device irradiates the optical recording medium with light having a small absorbance of the photochromic material through the optical system, and the refractive index of the light in the information recording state and the information unrecorded state in the optical recording medium. The information recording / reproducing (reading) / erasing device for the optical recording medium, wherein the information is reproduced (read) by detecting the difference between the two by the refractive index detecting device. (3) Information recording, reproducing (reading), and erasing device of the third optical recording medium The information recording area is made of a photochromic material, and the photochromic molecules in the recording area are oriented in a certain direction from the light source to the optical recording medium. Irradiating light to record information on the optical recording medium, reproduce (read) information from the optical recording medium, or erase information from the optical recording medium; An erasing device, a light source for information reproduction (reading), a light source for information erasing (or information recording), and a light source for emitting light of a constant wavelength having a large absorbance of the photochromic material; and a light from the light source. A polarization device that adjusts the light into a light having a polarization plane in a predetermined direction, a polarization control unit that controls the polarization device to adjust the direction of the polarization plane of the light, and light from the polarization device to the optical recording medium. An optical system for converging light on a body, and a refractive index detecting device for detecting a refractive index of light applied to the optical recording medium, for erasing information (or for recording information)
Adjusts the direction of the plane of polarization of light from the light source in the polarizing device under the control of the polarization control unit in a direction parallel to the direction of the transition moment of the photochromic molecule, and passes the light to the optical system. The information on the optical recording medium is erased by irradiating the optical recording medium through the optical recording medium (or information is recorded on the optical recording medium), and the information is reproduced (read) under the control of the polarization controller. Adjusting the direction of the polarization plane of the light from the light source in the polarizing device in a direction orthogonal to the direction of the transition moment of the photochromic molecules, and irradiating the light to the optical recording medium through the optical system, Information on an optical recording medium, wherein the difference in the refractive index of the light between the information recorded state and the unrecorded state in the optical recording medium is detected by the refractive index detection device to reproduce (read) the information. Recording, reproducing (reading), erasing device.

The optical recording medium used in the information recording, reproducing (reading) and erasing devices of the first to third optical recording media has an information recording area made of a photochromic material,
By utilizing the photochromic reaction, rewriting is possible by associating the state A and the state B of the photochromic material with the information unrecorded state and the information recorded state, or the information recorded state and the information unrecorded state, respectively.

In the information recording / reproducing (reading) / erasing apparatus for each of the first to third optical recording media, light having a wavelength in which the state A has absorption is used as information recording light (or erasing light).
Light having a wavelength at which the state B has absorption can be used as information erasing light (or recording light). In addition, light having a wavelength at which the photochromic material does not have absorption in both the states A and B, in other words, the wavelength at which the photochromic reaction hardly proceeds can be used as reproduction (reading) light.

According to the information recording, reproducing (reading) and erasing apparatus of the first optical recording medium, erasing of information on the optical recording medium whose information recording area is made of a photochromic material (or recording of information on the optical recording medium) ) And reproducing (reading) information from the optical recording medium, light having a certain fundamental wavelength is emitted from the same light source (light source for information reproducing (reading)). Light emitted from the light source enters the wavelength conversion device. Then, under the control of the wavelength control unit, light of a predetermined wavelength (including the case of light having the same wavelength as the fundamental wavelength of the light emitted from the light source) is emitted from the wavelength conversion device. When erasing information on an optical recording medium (or recording information on an optical recording medium) Light having a wavelength at which the photochromic material has a large absorbance under the control of the wavelength control unit from the wavelength conversion device, for example, the photochromic material A light having a wavelength having an absorption in the information recording state (or the information unrecorded state) is emitted, and the light is applied to the optical recording medium via the optical system. In the information recording area (or information non-recording area) of the optical recording medium irradiated with light, the light is easily absorbed, and the photochromic material changes from the information recording state (or information non-recording state) to the information non-recording state ( Or information recording state). Thereby, information on the optical recording medium is erased (or information is recorded on the optical recording medium). When reproducing (reading) information from an optical recording medium Under the control of the wavelength controller from the wavelength conversion device, light having a wavelength at which the absorbance of the photochromic material is small, for example, the information recording state of the photochromic material and the information Light of a wavelength having no absorption in the recording state is emitted. When light of a certain fundamental wavelength emitted from a reproduction (reading) light source can be used as it is as reproduction (reading) light, light of such a fundamental wavelength may be emitted from a wavelength conversion device. Light emitted from the wavelength converter is applied to the optical recording medium via the optical system. In the information recording area of the optical recording medium irradiated with light,
The light is hardly absorbed, and the photochromic reaction hardly proceeds. The light is reflected by the optical recording medium and is incident on the refractive index detecting device. The refractive index detecting device detects a difference in the refractive index of the light between the information recorded state and the information unrecorded state on the optical recording medium. Thereby, information is reproduced (read) from the optical recording medium.

In this information recording / reproducing (reading) / erasing apparatus for an optical recording medium, the light source for emitting the light having the predetermined fundamental wavelength is both an information reproducing (reading) light source and an information erasing light source. It is preferable to separately provide an information recording light source. When the light source is an information reproducing (reading) light source and an information recording light source, an information erasing light source may be separately provided. In this case, when recording information on the optical recording medium (or erasing information on the optical recording medium), light having a wavelength with a large absorbance of the photochromic material is supplied from a separately provided light source for information recording (or information erasing). For example, the optical recording medium is irradiated with light having a wavelength in which the information unrecorded state (or information recorded state) of the photochromic material has an absorption, and information is recorded on the optical recording medium (or the optical recording medium is Information will be erased).

According to the information recording / reproducing (reading) / erasing apparatus of the optical recording medium, light of a wavelength having a small absorbance of the photochromic material is reproduced (read) from the optical recording medium whose information recording region is made of a photochromic material. Since irradiation is performed as light, the progress of the photochromic reaction due to repeated irradiation of reproduction (read) light is suppressed, and even when the number of reproduction (read) is increased, destruction of recorded information on the optical recording medium is suppressed to reproduce (read). be able to. The light source for emitting the light having the constant fundamental wavelength is a light source for information reproduction (reading) and a light source for information erasing (or information recording), and includes a reproducing (reading) light and an erasing light (or recording light). Since the same light source is used, a recording, reproducing (reading) and erasing apparatus for an optical recording medium which is small and inexpensive can be manufactured.

Information recording and reproduction (reading) of the optical recording medium
In the erasing device, the wavelength conversion device is the light source.
Converts the fundamental wavelength of light from the laser into half and extracts the second harmonic
And the wavelength control unit includes a nonlinear optical member.
Phase Matching Condition for Wavelength Conversion by Nonlinear Optical Member
Can be exemplified. In this case, the wavelength conversion
The device is, for example, a device for polarizing light incident on the nonlinear optical member.
Includes a Faraday rotator to adjust the direction of the light plane
The wavelength control unit is based on the Faraday rotator.
By controlling the adjustment of the polarization direction of light, the nonlinear optical member
To control the phase matching condition for wavelength conversion
It may include a Ladder rotator control mechanism.
When such a wavelength conversion device and a wavelength control unit are adopted.
If the information reproducing (reading) light source is
One that can be used as it is as (reading) light
A light source that emits light having a constant fundamental wavelength can be employed. In addition, before
The non-linear optical member is not limited thereto,
Lithium niobate (LiNbO) _Three) Consisting of nonlinear optics
An element (SHG element) can be exemplified.

According to the information recording, reproducing (reading) and erasing apparatus of the second optical recording medium, erasing information on the optical recording medium whose information recording area is made of a photochromic material, recording information on the optical recording medium, In reproducing (reading) information from the optical recording medium, light having a constant fundamental wavelength is emitted from the same light source. Light emitted from the light source enters the wavelength conversion device. Then, under the control of the wavelength control unit, light of a predetermined wavelength (including light having the same wavelength as the fundamental wavelength of the light emitted from the light source) is emitted from the wavelength conversion device. When erasing information of the optical recording medium Light of a wavelength having a large absorbance of the photochromic material under the control of the wavelength control unit from the wavelength conversion device, for example, a wavelength of the information recording state of the photochromic material has an absorption. Light is emitted, and the light is applied to the optical recording medium via the optical system. In the information recording area of the optical recording medium irradiated with the light, the light is easily absorbed, and the photochromic material changes from the information recording state to the information non-recording state by a photochromic reaction. Thereby, the information on the optical recording medium is erased. When recording information on an optical recording medium Light having a large absorbance of the photochromic material under the control of the wavelength control unit from the wavelength conversion device, for example, a wavelength at which the information unrecorded state of the photochromic material has absorption. Is emitted to the optical recording medium via the optical system. In the information unrecorded area of the optical recording medium irradiated with the light, the light is easily absorbed, and the photochromic material changes from the information unrecorded state to the information recorded state by a photochromic reaction. Thereby, information is recorded on the optical recording medium. When reproducing (reading) information from an optical recording medium Under the control of the wavelength controller from the wavelength conversion device, light having a wavelength at which the absorbance of the photochromic material is small, for example, the information recording state of the photochromic material and the information Light of a wavelength having no absorption in the recording state is emitted. Light emitted from the wavelength converter is applied to the optical recording medium via the optical system. In the information recording area of the optical recording medium irradiated with the light, it is difficult to absorb the light,
The photochromic reaction hardly proceeds. The light is reflected by the optical recording medium and is incident on the refractive index detecting device. The refractive index detecting device detects a difference in the refractive index of the light between the information recorded state and the information unrecorded state on the optical recording medium. Thereby, information is reproduced (read) from the optical recording medium.

According to the information recording, reproducing (reading) and erasing apparatus of this optical recording medium, the light source for emitting light having a certain fundamental wavelength is a light source for information reproducing (reading) and a light source for information erasing and information recording. Yes, play (read)
Since the same light source is used for the light, the erasing light, and the recording light, the size and cost of the apparatus can be further reduced. In addition, as the light source, a light source that emits light having a constant fundamental wavelength that can be used as it is as information reproduction (read) light can be employed. In this case, when reproducing (reading) information, light having the same wavelength as the fundamental wavelength may be emitted from the wavelength converter.

In the second information recording / reproducing (reading) / erasing apparatus for an optical recording medium, the wavelength converter includes a parametric oscillator for converting a fundamental wavelength of light from the light source into a short wavelength. The wavelength control unit controls the phase matching condition and the parametric oscillator condition for wavelength conversion by the parametric oscillator. In this case, the wavelength conversion device may include a Faraday rotator for adjusting the direction of the plane of polarization of light incident on the device, and the wavelength control unit controls the direction of polarization of light by the Faraday rotator. A Faraday rotator control mechanism for controlling and controlling a phase matching condition for wavelength conversion by the parametric oscillator, and for determining a wavelength of wavelength-converted light by the parametric oscillator by controlling conditions of the parametric oscillator. A parametric oscillator condition control mechanism may be included. Even when such a wavelength conversion device and a wavelength control unit are employed, a light source that emits light of a certain fundamental wavelength that can be used as it is as information reproduction (read) light can be employed as the light source.

The wavelength conversion device in the information recording, reproducing (reading) and erasing devices of the first and second optical recording media is not limited to the one described above. The wavelength of the information unrecorded state of the photochromic material, a wavelength that has substantially no absorption in both the information recorded state and the information unrecorded state of the photochromic material, and a wavelength that can be converted to a wavelength in which either the information recorded state has absorption I just need. For example, the following can be mentioned. (A) A wavelength converter using an up-conversion glass (glass containing rare earth ions) that is excited by light having a wavelength λa and emits light having a wavelength λb shorter than the wavelength. (B) When a luminous body such as a fluorescent dye is excited by light having a wavelength λc, the luminous body emits its excitation energy in the form of fluorescence (wavelength λd), and the energy of the fluorescence is lower than the energy of the excitation light. Therefore, light having a longer wavelength λd than the excitation light (λc <λd) is obtained. Therefore, a wavelength converter using such a luminous body.

In the optical recording medium used for the information recording, reproducing (reading) and erasing apparatus of the third optical recording medium, photochromic molecules in the information recording area are oriented in a certain direction. Since the photochromic molecules in the recording area are aligned in a certain direction, the direction of the transition moment is also aligned in a certain direction. In this optical recording medium, if the electric field direction of the linearly polarized light of the light applied thereto is parallel to the direction of the transition moment of the photochromic molecule in the recording area, the light is easily absorbed by the recording area, but the transition moment If it is perpendicular to the direction, the light is hardly absorbed by the recording area.

The information recording / reproducing (reading) / erasing apparatus for the optical recording medium utilizes the properties of the optical recording medium. The photochromic material of the optical recording medium is not limited thereto, but may be a single crystal of a diarylethene-based compound. According to the information recording, reproducing (reading), and erasing device of the third optical recording medium,
When erasing information on the optical recording medium (or recording information on the optical recording medium) and reproducing (reading) information from the optical recording medium, the same light source (information reproducing (reading)) is used.
The light source emits a light having a constant fundamental wavelength at which the photochromic material has a large absorbance, for example, a wavelength having an absorption in the information recording state (or information non-recording state) of the photochromic material. Light emitted from the light source is incident on the polarizer, where it is adjusted to light having a plane of polarization in a predetermined direction. When erasing information on the optical recording medium (or recording information on the optical recording medium), the light emitted from the light source is controlled by the polarization control unit to change the polarization plane of the light from the light source in the polarizing device. The direction is adjusted in a direction parallel to the direction of the transition moment of the photochromic molecule. Light of a wavelength having a large absorbance of the photochromic material adjusted to light having a polarization plane in a predetermined direction by the polarizing device is applied to the optical recording medium via the optical system. In the information recording area (or information non-recording area) of the optical recording medium irradiated with light in which the direction of the polarization plane is adjusted in a direction parallel to the direction of the transition moment of the photochromic molecule, the light is easily absorbed,
The photochromic material changes from an information recorded state (or information unrecorded state) to an information unrecorded state (or information recorded state) by a photochromic reaction. As a result, information on the optical recording medium is erased (or information is recorded on the optical recording medium).
Is done. In the case of reproducing (reading) information from an optical recording medium, the light emitted from the light source is controlled by the polarization controller to change the direction of the plane of polarization of the light from the light source in the polarizing device. It is adjusted in the direction perpendicular to the direction of the moment. The light adjusted to light having a polarization plane in a predetermined direction by the polarizing device is applied to the optical recording medium via the optical system. In an information recording area of an optical recording medium irradiated with light whose polarization plane is adjusted in a direction orthogonal to the direction of the transition moment of the photochromic molecule, the light is hardly absorbed and the photochromic reaction hardly proceeds. The light is reflected by the optical recording medium and is incident on the refractive index detecting device. The refractive index detecting device detects a difference in the refractive index of the light between the information recorded state and the information unrecorded state on the optical recording medium. Thereby, information is reproduced (read) from the optical recording medium.

In this information recording / reproducing (reading) / erasing apparatus for an optical recording medium, the light source for emitting light of a constant fundamental wavelength having a large absorbance of the photochromic material is an information reproducing (reading) light source, and When the light source is an erasing light source, an information recording light source may be separately provided. When the light source is an information reproducing (reading) light source and an information recording light source, an information erasing light source may be separately provided. In recording information on the optical recording medium (or erasing information on the optical recording medium), a light having a large absorbance of the photochromic material from a separately provided information recording (or information erasing) light source, for example, The optical recording medium is irradiated with light having a wavelength at which the information unrecorded state (or information recorded state) of the photochromic material has an absorption, and information is recorded on the optical recording medium (or information on the optical recording medium is erased). Is done).

According to the information recording, reproducing (reading), and erasing apparatus of the optical recording medium, the information recording area is made of a photochromic material, and the photochromic molecules in the recording area are oriented in a certain direction. Light having a polarization plane in a direction in which the absorbance of the photochromic material is reduced, that is, light in which the direction of the polarization plane is adjusted to a direction orthogonal to the direction of the transition moment of the photochromic molecule is irradiated as reproduction (read) light. So
The progress of the photochromic reaction due to the repeated irradiation of the reproduction (read) light is suppressed, and the reproduction (read) can be performed while suppressing the destruction of the recorded information on the optical recording medium even if the number of reproduction (read) is increased. The light source which emits light having a constant fundamental wavelength having a large absorbance of the photochromic material, in other words, having an absorption in an information recording state (or in an information unrecorded state) is an information reproducing (reading) light source and an information erasing light source. (Or information recording) light source, and the same light source is used for reproduction (reading) light and erasing light (or recording light).
A reproduction (reading) and erasing device can be manufactured.

In this information recording / reproducing (reading) / erasing device for an optical recording medium, the polarizing device may include a Faraday rotator for adjusting the direction of the plane of polarization of light incident on the device. In this case, the wavelength control unit may include a Faraday rotator control mechanism for controlling adjustment of the polarization direction of light by the Faraday rotator.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram schematically showing an example of an information recording, reproducing (reading), and erasing apparatus for an optical recording medium according to the present invention. FIG. 2 is a functional block diagram of the device shown in FIG. In FIG. 2, the information recording light source 20, the optical system 300, the photodetector 40, and the like shown in FIG. 1 are not shown, and portions having the same configuration and operation are denoted by the same reference numerals.

As shown in FIGS. 1 and 2, a device for recording, reproducing and erasing information on an optical recording medium includes a laser light source 21, a wavelength converter 100, a wavelength controller 200, and an information recording device not shown in FIG. It includes a light source 20, an optical system 300, a photodetector 40, and a pinhole member 40a. Light emitted from the laser light source 21 enters the wavelength conversion device 100. Then, under the control of the wavelength control unit 200, light of a predetermined wavelength is emitted from the device 100. Apparatus 1
The light emitted from 00 is applied to the photochromic optical recording medium M via the optical system 300. Alternatively, the light is further reflected by the medium M, reenters the optical system 300, and enters the photodetector 40. The light emitted from the light source 20 is applied to the optical recording medium M via the optical system 300.

The photochromic optical recording medium M is an optical recording medium utilizing a photochromic reaction of a photochromic material, and comprises a glass substrate 41, an information recording layer 42, a metal reflective film 43, and a protective layer 44 as shown in FIG. I have. In this example, the optical recording medium M is obtained by mixing a diarylethene-based compound, which is a photochromic material, with a polystyrene resin on a glass substrate 41 and applying the mixture by spin coating to form an information recording layer 42. Further, after forming a metal reflection film 43 of aluminum or the like thereon, an ultraviolet curable resin is applied by spin coating and cured by ultraviolet light to form a protective layer 44.

FIG. 3 is a structural formula of a diarylethene compound which is a photochromic material used for the information recording layer of the optical recording medium M. FIG. 3 (A) shows the structural formula of the material in the state A. (B) shows the structural formula of the material in the state B. FIG. 4 is a diagram showing a light absorption spectrum of the material. In the drawing, a solid line indicates a change in the light absorption spectrum in the state A, and a dotted line in the figure indicates a change in the light absorption spectrum in the state B.

As shown in FIG. 4, according to the photochromic reaction of this photochromic material, the state of A (FIG. 3)
(See the structural formula of (A)).
By irradiating light having a wavelength λ1 in which the state A has absorption, for example, light having a wavelength of 365 nm, a state B (see the structural formula in FIG. 3B) having absorption of light having a different wavelength is generated. By irradiating the photochromic material in the state with light having a wavelength λ2 in which the state B has absorption, for example, a wavelength of 532 nm, the state returns to the original state A (see the structural formula in FIG. 3A).

In the optical recording medium M, by utilizing this reaction, in this example, the state A and the state B of the photochromic material correspond to the information unrecorded state and the information recorded state, respectively. In this information recording, reproducing and erasing apparatus for an optical recording medium, light having a wavelength λ1 (for example, 365 nm) can be used as information recording light, and light having a wavelength λ2 (for example, 532 nm) can be used as information erasing light. Further, light having a wavelength λ3 (for example, 1064 nm) at which the photochromic material does not have absorption in both the state A and the state B, in other words, where the photochromic reaction hardly proceeds, can be used as reproduction light.

The laser light source 21 shown in FIGS. 1 and 2 is an information reproducing light source and an information erasing light source. Therefore, information reproducing light and erasing light are emitted from the same laser light source 21. The light source 21 has a constant fundamental wavelength λ,
Light having a wavelength of 064 nm (output power: about 100 mW) can be emitted. The wavelength converter 100 includes a Faraday rotator 22 and a nonlinear optical element (SHG) which is an example of a nonlinear optical member.
Element 24). The Faraday rotator 22 can rotate the direction of the plane of polarization of the light emitted from the laser light source 21. The nonlinear optical element 24 is made of lithium niobate (LiNbO ₃ ) in this example, and can convert the light having the fundamental wavelength λ into the second harmonic having the wavelength λ / 2.

The wavelength control unit 200 includes a Faraday rotator control mechanism 23. Faraday rotator control mechanism 23
Can control the adjustment of the polarization direction of light by the Faraday rotator 22 to control the phase matching condition for wavelength conversion by the nonlinear optical element 24. Thereby, the wavelength conversion device 10
0 is the laser light source 21 under the control of the wavelength controller 200.
Light with a fundamental wavelength λ (1064 nm) from the
00 mW) is a predetermined wavelength, in this example, a wavelength λ2 (532 nm) that is used as information erasing light when the phase matching condition is satisfied.
= Wavelength λ / 2), and when the phase matching condition is not satisfied, the wavelength λ3 (1) is not converted to the second harmonic and is used as information reproduction light.
064 nm = the fundamental wavelength λ).

As shown in FIG. 1, the information recording light source 20
In this example, a laser light source that emits light having a wavelength of λ1 (365 nm) having absorption in the information unrecorded state (state A) of the photochromic material. The optical system 300 is a mirror 31,
It includes a power control element 32, a beam splitter 33, an objective lens 34, and a condenser lens 35. The mirror 31 can selectively reflect light of a specific wavelength. That is, the wavelength converter 1
The light from the light source 20 can be reflected and the light from the light source 20 can be transmitted and guided to the power control element 32, respectively. The power control element 32 can control the power of the light from the mirror 31. The beam splitter 33 can transmit light from the power control element 32 and guide the light to the lens 34. Further, light reflected from the optical recording medium M via the lens 34 can be guided to the photodetector 40 via the lens 35. The lens 34 is a beam splitter 33
Can be focused on a predetermined position of the optical recording medium M. Thereby, the optical system 300 can condense the light from the wavelength conversion device 100 or the light source 20 onto the optical recording medium M, and the light reflected from the optical recording medium M via the pinhole member 40a. Can be incident.

The pinhole member 4 disposed between the photodetector 40 and the front side thereof, that is, between the condensing lens 35.
0a constitutes an example of the refractive index detecting device. This pinhole member 40a is provided with a pinhole,
Since the photodetector 40 has the pinhole, the photodetector 40 detects only light incident on a predetermined position of the photodetector 40. Since the light reflected by the optical recording medium M is reflected to different positions according to the refractive index of the optical recording medium M as described later, the pinhole member is arranged so as to be incident on the pinhole at a predetermined refractive index. If this is done, it is possible to know (read) the difference in the refractive index of the optical recording medium M (whether the information is recorded or unrecorded) from the output signal of the photodetector. The photo detector 40 is used only for information reproduction,
Information on the detected light refractive index is sent to the information reproducing apparatus 400, where it is reproduced (read) to a desired final state.

FIG. 5 shows a refraction state of the reproduction light L in the optical recording medium M when reproducing information from the optical recording medium M.
As described above, the optical recording medium M shown in FIG. 5 has an information recording layer 42 formed on a glass substrate 41, a metal reflective film 43 formed thereon, and a protective layer 44 formed thereon.
In FIG. 5, the optical recording medium M is upside down.
When the photochromic material of the information recording layer 42 is in an information unrecorded state (state A), the reproduction light L is a solid-line reflected light LA.
When the information is recorded (state B),
The light is reflected like the broken light LB. The presence or absence of information recording on the optical recording medium M appears as a difference between the refractive index in the information recording state and the refractive index in the information unrecorded state, and here, it appears as a difference in the position of the reflected light.

According to the information recording / reproducing / erasing apparatus for the optical recording medium described above, the same light source 2 is used for erasing the information on the optical recording medium M and reproducing the information from the optical recording medium M.
From 1 light of the fundamental wavelength λ (1064 nm) is emitted.
The light emitted from the light source 21 is incident on the wavelength conversion device 100, where it is converted into light of a predetermined wavelength (including the case where the wavelength light emitted from the light source 21 remains unchanged). In the case of erasing the information on the optical recording medium M In the wavelength conversion device 100, the light emitted from the light source 21 is incident on the Faraday rotator 22, where the phase matching condition is controlled under the control of the Faraday rotator control mechanism 23. The polarization direction is adjusted so that the second harmonic is satisfied.
The light whose polarization direction has been adjusted is incident on the nonlinear optical element 24. The nonlinear optical element 24 converts the fundamental wave λ (1064 nm) of the light from the light source 21 into half, and extracts the second harmonic of the wavelength λ2 (532 nm) having an absorption in the information recording state (state B) of the photochromic material. It is. The light converted to the wavelength λ2 by the wavelength converter 100
00 is incident. In the optical system 300, the light converted to the wavelength λ2 is reflected by the mirror 31, and the power control element 32
The light passes through the beam splitter 33 and the objective lens 34 and is irradiated on the optical recording medium M for 0.1 μsec in this example. In the information recording layer of the optical recording medium M irradiated with the light of the wavelength λ2,
The light is easily absorbed, and the photochromic material changes from an information recorded state (state B) to an information unrecorded state (state A) by a photochromic reaction. Thereby, the information on the optical recording medium M is erased. In the case of reproducing information from the optical recording medium M In the wavelength converter 100, light emitted from the light source 21 is incident on the Faraday rotator 22, where the phase matching condition is controlled under the control of the Faraday rotator control mechanism 23. The polarization direction is adjusted so that the fundamental wave λ is obtained without being satisfied and not converted into the second harmonic. The light whose polarization direction has been adjusted is incident on the nonlinear optical element 24. Nonlinear optical element 2
4, the fundamental wave λ (1064 nm) of the light from the light source 21 is not converted and the information recording state (B
In this case, light having a wavelength λ3 (1064 nm = fundamental wave λ) having no absorption in both the information recording state and the information unrecorded state (state A) is output. Wavelength λ3 output from wavelength converter 100
Is incident on the optical system 300. In the optical system 300,
The light having the wavelength λ3 is reflected by the mirror 31 as in the information reproduction, passes through the power control element 32, the beam splitter 33, and the objective lens 34, and is irradiated to the optical recording medium M for 0.05 μsec in this example. In the information recording layer of the optical recording medium M irradiated with the light of the wavelength λ3, the light is hardly absorbed and the photochromic reaction hardly proceeds. The light is reflected by the optical recording medium M, passes through the lens 34 again, is reflected by the beam splitter 33, and is incident on the photodetector 40 via the condenser lens 35 and the pinhole member 40a. Photodetector 40 and pinhole member 40a
Detects the difference in the refractive index of the light between the information recorded state (state B) and the information unrecorded state (state A) on the optical recording medium M. The detected information is sent to the information reproducing device 400. Thereby, information is reproduced from the optical recording medium M. When information is recorded on the optical recording medium M In recording information on the optical recording medium M, light of a wavelength λ1 (365 nm) from the information recording light source 20 where the information unrecorded state (state A) of the photochromic material has absorption. Is incident on the optical system 300. In the optical system 300, the mirror 3
The light of wavelength λ1 that has passed through 1 is applied to the optical recording medium M in the same manner as when erasing and reproducing information. In the information recording layer of the optical recording medium M irradiated with light of the wavelength λ1, the light is easily absorbed, and the photochromic material changes from the information unrecorded state (state A) to the information recorded state (state B) by a photochromic reaction. Become. Thereby, information is recorded on the optical recording medium M.

According to the information recording / reproducing / erasing apparatus for the optical recording medium, the optical recording medium M whose information recording layer is made of a photochromic material is irradiated with light having a wavelength λ3 having a small absorbance of the photochromic material as reproduction light. So
The progress of the photochromic reaction due to repeated irradiation of the reproduction light is suppressed, and even if the number of reproductions increases, the reproduction can be performed while suppressing the destruction of the recorded information on the optical recording medium M. In addition, the light source 21 for emitting light having a constant fundamental wavelength λ is a light source for information reproduction and a light source for information erasure. Since the same light source is used for the reproduction light and the erasing light, recording on a small and inexpensive optical recording medium is correspondingly performed. , Reproducing and erasing devices.

It should be noted that information recording, reproduction,
In the erasing device, the state A and the state B of the photochromic material of the optical recording medium M may correspond to the information recorded state and the information unrecorded state, respectively. In this case, a light source for information reproduction and information recording is provided in place of the light source 21 for information reproduction and information erasing, and a light source for information erasing is provided in place of the light source 20 for information recording. 20
The wavelength conversion, such as 0, can be changed to accommodate it.

Next, another example of the information recording, reproducing (reading), and erasing apparatus of the optical recording medium according to the present invention is shown in FIG.
This will be described with reference to FIG. The information recording / reproducing / erasing apparatus of the optical recording medium shown in FIGS.
In the information recording / reproducing / erasing apparatus for an optical recording medium shown in (1), the recording light source 20 is removed, and a wavelength converter 100A and a wavelength controller 200A are provided instead of the wavelength converter 100 and the wavelength controller 200. The other points are the same as those used in the apparatus shown in FIGS. 1 and 2, and the portions having the same configuration and operation are denoted by the same reference numerals. The photochromic optical recording medium M used here is the same as that applied to the apparatus shown in FIGS.

The information recording / reproducing / erasing apparatus for the optical recording medium shown in FIGS. 6 and 7 will be described below focusing on the differences from the apparatus shown in FIGS. 1 and 2. As shown in FIGS. 6 and 7, the information recording, reproducing, and erasing apparatus for the optical recording medium uses the wavelength converter 100A to control the light emitted from the laser light source 21 under a predetermined control under the control of the wavelength controller 200A. The light is converted into light having a wavelength, and is applied to the photochromic optical recording medium M via an optical system 300 not shown in FIG. Alternatively, the light is further reflected by the medium M. The light reflected on the optical recording medium M is again incident on the optical system 300 and enters the photodetector 40.

The laser light source 21 is a light source for information reproduction and a light source for information erasing and recording. Therefore, all of the information recording light, reproduction light and erasing light are emitted from the same laser light source 21. The light source 21 emits light having a constant fundamental wavelength λ, 1064 nm in this example (output power of about 100 m).
W) can be injected. The wavelength conversion device 100A includes a Faraday rotator 22A and a parametric oscillator 25. The Faraday rotator 22A can rotate the direction of the polarization plane of the light emitted from the laser light source 21. The parametric oscillator 25 can convert light having the fundamental wavelength λ into short-wavelength light.

The wavelength control unit 200A includes a Faraday rotator control mechanism 23A and a parametric oscillator condition control mechanism 26.
Contains. The Faraday rotator control mechanism 23 </ b> A controls the adjustment of the polarization direction of light by the Faraday rotator 22 and can control the phase matching condition for wavelength conversion by the parametric oscillator 25. The parametric oscillator condition control mechanism 26 can determine the wavelength of the wavelength-converted light by the parametric oscillator 25 by controlling the condition of the parametric oscillator 25. Accordingly, the wavelength converter 100A controls the light of the fundamental wavelength λ (1064 nm) (the output power of about 100 m) from the laser light source 21 under the control of the wavelength controller 200A.
W) is a predetermined wavelength, in this example, a wavelength λ that is used as information recording light (output power about 5 mW) when the phase matching condition is satisfied.
1 (410 nm in this example) or a wavelength λ2 (532 nm in this example) at which information is erased (output power: about 10 mW).
When the phase matching condition is not satisfied, light of wavelength λ3 (1064 nm = fundamental wavelength λ) can be output as information reproduction light without being converted to short wavelength light.

According to the apparatus for recording, reproducing and erasing information on the optical recording medium, erasure of information on the optical recording medium M,
In recording information to the optical recording medium M and reproducing information from the optical recording medium M, the same light source 21 outputs the fundamental wavelength λ (1064 nm).
Light is emitted. The light emitted from the light source 21 is incident on the wavelength conversion device 100A, where it is converted into light of a predetermined wavelength (including the case where the wavelength light emitted from the light source 21 remains unchanged). In the case of erasing information on the optical recording medium M In the wavelength conversion device 100A, light emitted from the light source 21 is incident on the Faraday rotator 22A, where the phase matching condition is controlled under the control of the Faraday rotator control mechanism 23A. The polarization direction is adjusted so that the short-wavelength light is obtained. The light whose polarization direction has been adjusted is a parametric oscillator 2
5 is incident. The parametric oscillator 25 is controlled by a parametric oscillator condition control mechanism 26 so as to obtain light having a wavelength that acts as light for erasing information. The fundamental wave λ (1064 nm) of light from the light source 21 is converted by the parametric oscillator 25 into short-wavelength light (light having a wavelength acting as erasing light) having a wavelength λ2 (532 nm) at which the information recording state of the photochromic material has absorption. You. The light converted to the wavelength λ2 by the wavelength conversion device 100A passes through the optical system 300 and, in this example, the optical recording medium M of 0.1 μsec.
Is irradiated. Optical recording medium M irradiated with light of wavelength λ2
In the information recording layer, the light is easily absorbed, and the photochromic material changes from an information recorded state to an information unrecorded state by a photochromic reaction. Thereby, the information on the optical recording medium M is erased. In a case where information is recorded on the optical recording medium M In the wavelength conversion device 100A, the light emitted from the light source 21 is incident on the Faraday rotator 22A, and the phase matching condition is controlled under the control of the Faraday rotator control mechanism 23A. The polarization direction is adjusted so that the short-wavelength light is obtained. The light whose polarization direction has been adjusted is a parametric oscillator 2
5 is incident. The parametric oscillator 25 is controlled by a parametric oscillator condition control mechanism 26 so that light having a wavelength acting as information recording light is obtained. The fundamental wave λ (1064 nm) of the light from the light source 21 is converted by the parametric oscillator 25 into short-wavelength light (light having a wavelength acting as recording light) having a wavelength λ1 (410 nm) in which the information unrecorded state of the photochromic material has absorption. Is done. The light converted to the wavelength λ1 by the wavelength converter 100A is applied to the optical recording medium M via the optical system 300 in this example for 0.2 μsec. In the information recording layer of the optical recording medium M irradiated with the light of the wavelength λ1, the light is easily absorbed, and the photochromic material changes from an unrecorded state to an information recorded state by a photochromic reaction. Thereby, information is recorded on the optical recording medium M. When Reproducing Information from Optical Recording Medium M In the wavelength conversion device 100A, light emitted from the light source 21 is incident on the Faraday rotator 22A, where the phase matching condition is controlled under the control of the Faraday rotator control mechanism 23A. The polarization direction is adjusted so that the fundamental wave λ is obtained without being satisfied and not converted into short-wavelength light. The light whose polarization direction has been adjusted is incident on the parametric oscillator 25. In the parametric oscillator 25, the fundamental wave λ of the light from the light source 21
(1064 nm) is output without conversion at a wavelength λ3 (1064 nm = fundamental wave λ) that has no absorption in both the information recorded state and the information unrecorded state of the photochromic material. In the present example, the light of wavelength λ3 output from the wavelength conversion device 100A is applied to the optical recording medium M via the optical system 300 for 0.05 μsec. In the information recording layer of the optical recording medium M irradiated with the light of the wavelength λ3, the light is hardly absorbed and the photochromic reaction hardly proceeds. The light is reflected by the optical recording medium M, reenters the optical system 300, and enters the photodetector 40.

According to the apparatus for recording, reproducing and erasing information on the optical recording medium described above, the laser light source 21 is a light source for information reproduction and also a light source for information erasure and information recording. Since the same light source is used for the light, the size and cost of the device can be further reduced. Next, still another example of the information recording, reproducing (reading), and erasing apparatus of the optical recording medium according to the present invention will be described with reference to FIGS.

The information recording / reproducing / erasing apparatus for the optical recording medium shown in FIGS. 8 and 9 is the same as the information recording / reproducing / erasing apparatus for the optical recording medium shown in FIGS. Light source 20, laser light source 21, wavelength converter 10
0 and the photochromic optical recording medium M ′, the information recording light source 20 ′, and the laser light source 2 in place of the wavelength control unit 200.
1 ′, a polarization device 100B and a polarization control unit 200B are provided. The other points are the same as those of the apparatus shown in FIGS. 1 and 2, and the portions having the same configuration and operation are denoted by the same reference numerals.

The information recording / reproducing / erasing apparatus for the optical recording medium shown in FIGS. 8 and 9 will be described below focusing on the differences from the apparatus shown in FIGS. 1 and 2. The photochromic optical recording medium M ′ used in the information recording, reproducing, and erasing apparatus of this optical recording medium is made of a photochromic material in the same manner as the photochromic optical recording medium M used in the apparatuses shown in FIGS. 1 and 2 and FIGS. This is an optical recording medium utilizing a photochromic reaction. In this example, the state A and the state B of the photochromic material correspond to an information unrecorded state and an information recorded state, respectively. As the optical recording medium M ′, a single crystal of a diarylethene-based compound shown in FIG. 3 is used for the information recording layer of the medium. As a single crystal of the information recording layer, a solution prepared by dissolving the diarylethene-based compound in methanol at 50 ° C. to prepare a saturated solution and then leaving the solution to reach room temperature (size: about 3 mm square) is used.

The optical recording medium M 'has photochromic molecules in the information recording layer oriented in a certain direction. Since the photochromic molecules in the recording layer are aligned in a certain direction, the direction of the transition moment is also aligned in a certain direction.
In this optical recording medium, if the electric field direction of the linearly polarized light of the light applied thereto is parallel to the direction of the transition moment of the photochromic molecules in the recording layer, the light is easily absorbed by the recording layer, but the transition moment If it is perpendicular to the direction, the light is hardly absorbed by the recording layer.

The information recording / reproducing / erasing apparatus for the optical recording medium utilizes the properties of the optical recording medium. The laser light source 21 'is a light source for information reproduction and a light source for information erasure. Therefore, information reproducing light and erasing light are emitted from the same laser light source 21 '. The light source 21 'can emit light having a constant fundamental wavelength at which the absorbance of the photochromic material is large, in this example, a wavelength λ2 (514 nm) at which the information recording state of the photochromic material has absorption.

The polarizer 100B is a Faraday rotator 22
B. The Faraday rotator 22B can rotate the direction of the polarization plane of the light emitted from the laser light source 21 '. The polarization control unit 200B includes a Faraday rotator control mechanism 23B. The Faraday rotator control mechanism 23B can control the adjustment of the polarization direction of light by the Faraday rotator 22B.

As shown in FIG. 8, the information recording light source 20 '
Is the wavelength λ1 at which the information unrecorded state has absorption in this example.
(365 nm). According to the information recording, reproducing and erasing apparatus for the optical recording medium, when erasing information from the optical recording medium M ′ and reproducing information from the optical recording medium M, the absorbance of the photochromic material from the same light source 21 ′ is large (information (With absorption of recording state)
Light having a constant fundamental wavelength λ2 (514 nm) is emitted. The light emitted from the light source 21 ′ is incident on the polarization device 100B, where it is adjusted to light having a polarization plane in a predetermined direction. When erasing information from optical recording medium M 'In the polarization device 100B, the direction of the polarization plane of the light emitted from the light source 21' is controlled by the Faraday rotator 22B under the control of the Faraday rotator control mechanism 23B. It is adjusted in a direction parallel to the direction of the transition moment. The wavelength λ2 (5) at which the information recording state adjusted to light having a polarization plane in a predetermined direction by the polarization device 100B has absorption.
14 nm) linearly polarized light (output power 10 mW)
The light is applied to the optical recording medium M for 0.1 μsec. The wavelength λ2 (514) in which the direction of the polarization plane is adjusted in a direction parallel to the direction of the transition moment of the photochromic molecule.
nm) of the information recording layer of the optical recording medium M ′ irradiated with the light, the light is easily absorbed, and the photochromic material changes from an information recorded state to an information unrecorded state by a photochromic reaction. Thereby, the information on the optical recording medium M 'is erased. In the case of reproducing information from the optical recording medium M 'In the polarization device 100B, the direction of the polarization plane of the light emitted from the light source 21' is controlled by the Faraday rotator 22B under the control of the Faraday rotator control mechanism 23B. It is adjusted in a direction orthogonal to the direction of the transition moment. The linearly polarized light (output power: 5 mW) of the wavelength λ2 (514 nm) adjusted to light having a polarization plane in a predetermined direction by the polarization device 100B is transmitted through the optical system 300 for 0.05 μsec.
Irradiation is performed on the optical recording medium M ′. An optical recording medium M ′ irradiated with light having a wavelength λ2 in which the direction of the polarization plane is adjusted in a direction orthogonal to the direction of the transition moment of the photochromic molecule.
In the information recording layer, the light is hardly absorbed, and the photochromic reaction hardly proceeds. The light is reflected by the optical recording medium M ′, reenters the optical system 300, and enters the photodetector 40. The photodetector 40 and the pinhole member 40a detect the difference in the refractive index of the light between the information recorded state and the information unrecorded state on the optical recording medium M '. Thereby, information is reproduced from the optical recording medium M ′. In the case of recording information on the optical recording medium M ′ In recording information on the optical recording medium M ′, light having a wavelength λ1 (365 nm) from the information recording light source 20 ′ where the information unrecorded state of the photochromic material has absorption is optically. System 30
It is incident on zero. In the optical system 300, the light having the wavelength λ1 transmitted through the mirror 31 is applied to the optical recording medium M ′ in the same manner as when erasing and reproducing information. In the information recording layer of the optical recording medium M ′ irradiated with the light having the wavelength λ1, the light is easily absorbed, and the photochromic material changes from an unrecorded state to an information recorded state by a photochromic reaction. Thus, information is recorded on the optical recording medium M ′.

According to the information recording / reproducing / erasing apparatus of this optical recording medium, the information recording layer is made of a photochromic material, and the optical recording medium M ′ in which the photochromic molecules in the recording layer are oriented in a certain direction. Light having a polarization plane in a direction such that the absorbance of the photochromic material decreases, that is, light in which the direction of the polarization plane is adjusted in a direction orthogonal to the direction of the transition moment of the photochromic molecule is irradiated as reproduction light, so that the reproduction light The progress of the photochromic reaction due to repeated irradiation is suppressed, and even if the number of times of reproduction is increased, the reproduction can be performed while suppressing the destruction of the information recorded on the optical recording medium M ′. In addition, the light source 21 'which emits light having a constant fundamental wavelength λ2 having an absorption in the information recording state is a light source for information reproduction and a light source for information erasing. Since the same light source is used for the reproduction light and the erasing light, the light source is compact. Thus, an inexpensive recording, reproducing and erasing apparatus for an optical recording medium can be manufactured.

It should be noted that information recording, reproduction,
In the erasing device, the states A and B of the photochromic material of the optical recording medium M ′ may correspond to the information recorded state and the information unrecorded state, respectively. In this case, an information reproducing and information recording light source can be provided in place of the information reproducing and information erasing light source 21 ', and an information erasing light source can be provided in place of the information recording light source 20'.

In this embodiment, the refractive index detector detects the difference in the reflection position of the reproduction light by irradiating the reproduction light obliquely to the optical recording medium. The light may be incident and the phase of the reflected light may be detected.

[0054]

According to the present invention, by irradiating light from a light source to an optical recording medium whose information recording region is made of a photochromic material, information is recorded on the optical recording medium and information is reproduced from the optical recording medium. Or an information recording / reproducing / erasing apparatus for an optical recording medium for erasing information on the optical recording medium, which does not require a separate light source exclusively for information reproduction, and reproduces information while suppressing destruction of recorded information. Therefore, it is possible to provide an information recording / reproducing / erasing apparatus for an optical recording medium capable of achieving downsizing and cost reduction of the apparatus.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an example of an apparatus for recording, reproducing, and erasing information on an optical recording medium according to the present invention.

FIG. 2 is a functional block diagram of the information recording, reproducing, and erasing apparatus for the optical recording medium shown in FIG.

FIG. 3 is a structural formula of a diarylethene-based compound that is a photochromic material used for an information recording layer of an optical recording medium, and FIG. 3A is a structural formula of the material in an unrecorded state (state A); Figure (B) shows the information recording state of the material (B
State).

FIG. 4 is a diagram showing a light absorption spectrum of the photochromic material shown in FIG.

FIG. 5 is a diagram showing a refraction state of reproduction light in the optical recording medium when information is reproduced from the optical recording medium.

FIG. 6 shows information recording, reproduction, and the like of the optical recording medium according to the present invention.
It is another example of the erasing device.

FIG. 7 is a functional block diagram of the information recording / reproducing / erasing device of the optical recording medium shown in FIG. 6;

FIG. 8 shows information recording, reproduction, and the like of the optical recording medium according to the present invention.
It is another example of the erasing device.

FIG. 9 is a functional block diagram of the information recording / reproducing / erasing device for the optical recording medium shown in FIG.

[Explanation of symbols]

20, 20 'Information recording light source 21, 21' Laser light source 22, 22A, 22B Faraday rotator 23, 23A, 23B Faraday rotator control mechanism 24 Nonlinear optical element (one example of nonlinear optical member) 25 Parametric oscillator 26 Parametric oscillator Condition control mechanism 31 Mirror 32 Power control element 33 Beam splitter 34 Objective lens 35 Condensing lens 40 Photodetector (1 of an example of a refractive index detecting device)
Part) 40a pinhole member 41 glass substrate 42 information recording layer 43 metal reflection film 44 protective layer 100, 100A wavelength converter 100B polarizer 200, 200A wavelength controller 200B polarization controller 300 optical system 400 information reproducing device M, M ' Photochromic optical recording medium λ1 Information recording light wavelength λ2 Information erasing light wavelength λ3 Information reproducing light wavelength

Continuation of the front page F term (reference) 5D029 HA05 JA04 JC03 JC06 VA03 5D090 BB04 CC01 CC04 CC16 CC18 DD01 DD05 FF09 FF34 5D119 AA05 AA26 BB06 DA01 DA05 DA07 HA64 JB03 KA12

Claims (5)

[Claims] 1. An optical recording medium whose information recording area is made of a photochromic material is irradiated with light from a light source to record information on the optical recording medium, reproduce information from the optical recording medium, or read information from the optical recording medium. Information recording on an optical recording medium for erasing information,
In a reproducing and erasing apparatus, a light source for emitting light of a constant fundamental wavelength, which is a light source for information reproduction and a light source for information erasing (or information recording), and converts the wavelength of light from the light source to a predetermined wavelength. A wavelength converter, a wavelength controller that controls wavelength conversion of light by the wavelength converter, an optical system for condensing light from the wavelength converter on the optical recording medium, and the optical recording medium. A refraction index detecting device for detecting a refraction index of irradiated light, and when erasing information (or recording information), the wavelength conversion device controls the photochromic device under the control of the wavelength control unit. The information is erased (or information is recorded) by irradiating the optical recording medium with light having a wavelength having a large absorbance of the material through the optical system, and when the information is reproduced, the control by the wavelength control unit is also performed. And the wavelength Irradiating the optical recording medium with light of a wavelength having a small absorbance of the photochromic material from the switching device via the optical system, and the difference in the refractive index of the light between the information recorded state and the information unrecorded state in the optical recording medium The information recording / reproducing / erasing device for an optical recording medium, wherein the information is reproduced by detecting the information with the refractive index detecting device. 2. The wavelength conversion device includes a nonlinear optical member for converting a fundamental wavelength of light from the light source into half to extract a second harmonic, and the wavelength control unit performs wavelength conversion by the nonlinear optical member. 2. The information recording / reproducing of the optical recording medium according to claim 1, wherein the phase matching condition is controlled.
Erasing device. 3. An optical recording medium whose information recording area is made of a photochromic material is irradiated with light from a light source to record information on the optical recording medium, reproduce information from the optical recording medium, or read information from the optical recording medium. Information recording on an optical recording medium for erasing information,
In a reproducing and erasing apparatus, a light source for emitting light having a constant fundamental wavelength, which is both a light source for information reproduction and a light source for information erasing and information recording, and a wavelength converter for converting a wavelength of light from the light source to a predetermined wavelength. A device, a wavelength controller for controlling wavelength conversion of light by the wavelength converter, an optical system for condensing light from the wavelength converter on the optical recording medium, and irradiating the optical recording medium. And a refractive index detecting device for detecting the refractive index of the light.
Information is erased by irradiating the optical recording medium with erasing light having a large absorbance of the photochromic material from the wavelength converter under the control of the wavelength control unit through the optical system, thereby recording information. At the time, information is recorded by irradiating the optical recording medium through the optical system with recording light having a large absorbance of the photochromic material from the wavelength conversion device under the control of the wavelength control unit, At the time of reproducing information, the optical recording medium is irradiated with light having a small wavelength of absorbance of the photochromic material from the wavelength conversion device through the optical system under the control of the wavelength control unit. Wherein the difference between the refractive index of the light in the information recorded state and the refractive index of the light in the unrecorded state is detected by the refractive index detecting device to reproduce the information. Recording, playback, erasing apparatus. 4. The wavelength converter includes a parametric oscillator for converting a fundamental wavelength of light from the light source into a short wavelength, and the wavelength controller includes a phase matching condition and a parametric condition for wavelength conversion by the parametric oscillator. 4. An apparatus for recording, reproducing and erasing information on an optical recording medium according to claim 3, wherein said apparatus controls an oscillator condition. 5. An information recording area is made of a photochromic material, and light from a light source is irradiated to an optical recording medium in which photochromic molecules in the recording area are oriented in a fixed direction to record information on the optical recording medium. An information recording, reproducing, and erasing device for an optical recording medium for reproducing information from the optical recording medium or erasing information from the optical recording medium, and is an information reproducing light source and also for information erasing (or information recording). A light source that emits light of a constant wavelength having a large absorbance of the photochromic material; a polarizing device that adjusts light from the light source to light having a polarization plane in a predetermined direction; and a polarization plane of light by the polarization device. A polarization controller for controlling the adjustment of the direction of the light, an optical system for condensing the light from the polarizing device on the optical recording medium, and a refraction for detecting a refractive index of the light applied to the optical recording medium. rate When erasing information (or recording information), the polarization device controls the polarization plane of light from the light source in the polarization device under the control of the polarization controller. The information on the optical recording medium is erased by adjusting the direction of the transition moment in a direction parallel to the direction of the transition moment and irradiating the optical recording medium with the light through the optical system (or information is recorded on the optical recording medium). At the time of reproducing information, the direction of the plane of polarization of the light from the light source is adjusted in the polarizing device in a direction orthogonal to the direction of the transition moment of the photochromic molecule under the control of the polarization control unit. Is irradiated on the optical recording medium through the optical system, and the difference in the refractive index of the light between the information recorded state and the information unrecorded state on the optical recording medium is detected by the refractive index detecting device to reproduce the information. You That the information recorded in the optical recording medium characterized, reproducing, erasing apparatus.