JPS63308732A - Method for erasing optical recording - Google Patents

Abstract

PURPOSE:To enable local erasing with a photochemical hole burning PHB memory for which a hole burning phenomenon is used by projecting continuous light of a required wavelength on the memory, thereby erasing the recording. CONSTITUTION:Laser light of a narrow beam width is wavelength-swept stepwise at wavelength intervals of about 5 times the beam width in the nonuniform absorption spectra of a material which allows PHB recording, by which holes are formed and the recording is executed. The hole formation is then executed uniformly and continuously over the entire part of the corresponding molecules when the continuous laser light of the wavelength range used for the recording is projected. The nonuniform spectra similar to the nonuniform spectra in the unrecorded state are thereby applied and the local erasing is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to wavelength multiplexed optical recording with high recording density, and particularly to a method for erasing optical recording using hole burning phenomenon.

[Conventional technology]

The challenges in information recording and reproducing methods using light are to improve recording density, rewritability, and input/output speed. In order to address the above-mentioned problems, in recent years, research has been actively conducted to search for new optical recording media and to wavelength multiplexing using multilayer structures. Among these, one that is attracting attention as a future information storage means is PHB memory (Photo chemical
hole burning memory). The hole burning phenomenon described above is academically interesting and is known as one of high-resolution spectroscopy methods. The above recording method was proposed by IBM in 1978 (Japanese Patent Application Laid-Open No. 53-997
35), is a wavelength multiplexing optical memory that is expected to significantly improve recording density by about 1000 times that of conventional types. The principle will be described below.

When a photochemically active molecule is placed in a cold solid matrix, its absorption spectrum reflects subtle differences in the environment in which the molecule is placed, resulting in a non-uniform structure as shown in Figure 2(a). By irradiating a high-intensity laser beam with a narrow linewidth at a specific wavelength λ within the spectrum, which indicates the spectral width, only molecules that resonate with the wavelength λ absorb the light and pass through the excited state. Then, it moves to a metastable state different from the initial ground state. The above metastable state is i
) Proton movement within a molecule due to light absorption, ii) Change in the orientation of molecules in a matrix due to light absorption, and ■) Photodissociation of molecules due to light absorption. When the above metastable state is maintained, a decrease in the absorption intensity is observed only at the wavelength λ1 of light irradiation, as shown in Figure 2(b), and a hole with a sharp spectral width appears on the absorption spectrum.
I can m. Furthermore, as shown in FIG. 2(0), the wavelength of light irradiation is sequentially changed to λ3. By changing λ, . . . and forming holes, a wavelength multiplexed optical memory can be formed.

As mentioned above, PHB memory is based on the basic principle of subtle state changes induced by light, so it is difficult to record data.

In other words, it is necessary to pay sufficient attention to the stability of holes in the absorption spectrum, and in fact, when the temperature of the recording medium is 2.
It is known that when the temperature rises to 0 to 30K, optically recorded holes cannot be stably held and the holes disappear. Therefore, the entire recording medium used in PHB memory is liquid helium, which has a temperature of 4.2
Currently, it is stored at extremely low temperatures.

[Problem that the invention seeks to solve]

As mentioned above, research on PHB memory is being conducted under strict conditions to investigate recording mechanisms and recording media. However, as for methods of erasing records, although it is possible to erase the entire recording medium at a high temperature by heating it all at once, until now there has been almost no solution to locally erasing a part of the recording medium. situation.

The object of the present invention is to obtain a method that allows locally erasing records in a PHB memory under cryogenic conditions.

[Means for solving problems]

The above object is achieved by irradiating the recorded portion of the PHB memory with white light in the wavelength range used for recording, or by continuously irradiating the wavelength range to be erased with laser light while sweeping the wavelength.

[Effect]

In the non-uniform absorption spectrum of PHB recordable substances,
A laser beam with a narrow line width is wavelength-swept stepwise at a wavelength interval of about 5 times the line width to perform recording (hole formation).Next, for the same laser spot recorded in the PHB above,
Irradiate white light in the wavelength range used for recording. Alternatively, the wavelength range to be erased is irradiated with a laser beam while continuously sweeping the wavelength. Through the above operation, holes are uniformly and continuously formed throughout the molecules (or recording medium) whose absorption corresponds to the wavelength range irradiated with light for erasing, that is,
The delicate environment of molecules in the medium is rearranged, giving a non-uniform spectrum similar to the unrecorded state, and the PHB recording is erased.

The above phenomenon occurs locally only within the spot irradiated with the erasing light, and does not affect the surrounding recorded areas in any way.

It is also possible to re-record the portion erased by the above method. Therefore, it is possible to erase and rewrite records on a portion of the recording medium (any laser spot). Further, by arbitrarily selecting the sweep wavelength range of the erasing laser beam, it is possible to partially erase and rewrite records on the wavelength axis within one laser spot.

Furthermore, the erasing method of the present invention can be easily carried out when the hole formation mechanism is a photo-induced molecular orientation change or a subtle structural change in the recording medium. Furthermore, it can be widely applied not only to organic materials mainly composed of organic molecules such as porphyrin and quinizarin, but also to inorganic materials such as color centers of alkali halide crystals, which are considered promising for compatibility with semiconductor lasers.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the optical recording erasing method according to the present invention, in which (a) is the chemical formula of the dye molecule constituting the recording medium, (b') is the absorption spectrum of the recording medium, and (c) is the diagram. Absorption spectrum showing PHB memory after recording (before erasing),
(d) is a diagram showing absorption spectra showing the PHB memory after the erase operation. A recording medium was prepared by dispersing 1,4-dihydroxyanthraquinone (commonly known as quinizarine, DAQ), whose chemical formula is shown in FIG. Saved at 4.2K. The absorption spectrum of the recording medium is as shown in FIG. 1(b), indicating absorption due to DAQ. First, using a wavelength tunable dye laser, we
A hole was formed in the nm absorption band, and optical recording of a PHB memory consisting of the binary code shown in FIG. 1(c) was performed.

Next, in order to erase the record, the same wavelength variable color laser used for recording was applied to the recorded part of laser spot 1-.
Irradiation was performed while continuously sweeping the wavelength in the wavelength range of 510 to 515 nm. As a result, P formed in the absorption band of DAQ
As shown in FIG. 1(d), the holes in the HB memory disappeared almost completely, and erasure of the PHB memory was achieved. In addition,
It was also possible to re-record to the erased area.

〔Effect of the invention〕

As described above, the optical recording erasing method according to the present invention irradiates the recording based on the hole burning of an optical recording medium made of a material capable of hole burning by light irradiation with light having a continuous wavelength within the wavelength range used for the recording. By erasing the recording, it is possible to selectively erase only a predetermined portion of the PHB memory without adjusting the temperature of the recording medium, and it is possible to perform recording again after erasing. be.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the optical record erasing method according to the present invention, in which (a) is the chemical formula of the dye molecules constituting the recording medium, (b) is the absorption spectrum of the recording medium, and (C) is the recording Absorption spectrum showing the PHB memory after (before erasing), (
d) is a diagram showing the absorption spectrum of the PHB memory after erasing operation, and Figure 2 is a diagram explaining the basic principle of the conventional PHB memory. (a) is the absorption spectrum of a photochemically active molecule; (b) is an absorption spectrum showing hole burning due to laser light irradiation, and (C) is a diagram showing a wavelength multiplexed optical memory in which holes are formed by changing the light irradiation wavelength. Representative Patent Attorney Junnosuke Nakamura 1P1 Zouzu Chief Member? FL)

Claims (1)

[Claims] 1. For recording based on the hole burning described above on an optical recording medium made of a substance capable of hole burning by light irradiation,
An optical record erasing method in which the record is erased by irradiating light with a continuous wavelength within the wavelength range used for the record. 2. The optical record erasing method as set forth in claim 1, wherein the continuous wavelength light is white light. 3. The light of claim 1, wherein the continuous wavelength light is a laser light, and the laser light is continuously irradiated while sweeping the wavelength range to be erased. How to delete records.