JPS59195228A - Two-layered type optical memory and its recording and reproducing system - Google Patents

Abstract

PURPOSE:To obtain a two-layered type optical memory which is suitable for high- density, high-speed recording and reproducing operation by laminating the 1st transparent conductive film, thin electrochromic film, photoconductive film, the 2nd transparent thin film, and thin film for photomagnetic recording successively. CONSTITUTION:The two-layered type optical memory 1 consists of the transparent substrate 2, transparent conductive film 3, electrochromic (EC) film 4, photoconductive film 5, transparent conductive film 6, and thin (MO) film 7 for photomagnetic recording. A voltage V modulated corresponding to the 1st digital signal is applied between the transparent conductive films 3 and 6 and a magnetic field H modulated corresponding to the 2nd digital signal is applied to the MO film 7. Laser light 8 with a specific quantity P is converted in discrete time series to focus and illuminate a recording position on the MO film 7 through a polarizer 9. Only the part is magnetized in a direction H by a temperature rise. Its transmitted light make the irradiated part of the photoconductive film 5 conductive and V is applied to the EC film 4 corresponding to the part to color the film 4. Thus, the memory which suits to the high-density, high- speed recording and reproducing operation is obtaind.

Description

DETAILED DESCRIPTION OF THE INVENTION (Object of the Invention) The present invention relates to a two-layer optical memory, its recording method, and its reproducing method.

(Objective of the Invention) The present invention has double the recording capacity compared to conventional optical memory.
It is an object of the present invention to provide a two-layer optical memory capable of simultaneously recording and reproducing two digital data in parallel, and in which the recorded digital data can be changed and recorded without erasing it, its recording method, and its reproducing method. purpose.

(Contents of conventional examples and their drawbacks) In recent years, development of media, devices, etc. for recording and reproducing information has been active. Among these, magneto-optical recording, which performs recording and reproduction by irradiating a magneto-optical recording material with a laser beam, has been attempted. A memory with sufficient performance has not yet been realized.

(Means for solving the problems) In order to solve the above-mentioned problems, the present invention provides a transparent substrate,
a first transparent conductive film formed on the transparent substrate; an electrochromic thin film for recording a first digital signal formed on the first transparent conductive film; and a photoconductive film formed on the electrochromic thin film. and a second transparent conductive film formed on the photoconductive film, and a magneto-optical recording thin film for recording a second digital signal formed on the second transparent conductive film. .

(Embodiment of the invention) Fig. 1 is a diagram for explaining the structure and operation of an embodiment of a two-layer optical memory according to the invention, and Fig. 2 (A), (B), and (C).
is a diagram showing time-series changes in light, voltage, and magnetic field applied to the two-layer optical memory shown in Fig. 1, and Fig. 3 (A) and (B) are diagrams showing the time-series changes in the light, voltage, and magnetic field applied to the two-layer optical memory shown in Fig. 1. FIG. 3 is a diagram showing time-series changes in signal output.

As shown in FIG. 1, a two-layer optical memory 1 includes a thin film of indium oxide (Indium oxide) on a transparent substrate 2 such as a glass substrate.
The transparent conductive film 3, which is the first transparent conductive film using a semiconductor thin film such as um Tin Oxido (hereinafter referred to as ITO film), has two states of optical absorption characteristics in the visible light region: transparent and colored, A thin film that exhibits an electrochromic phenomenon in which these two states can be reversibly selected by electrical energy, such as an electrochromic film (elrochromic film) using a tungsten trioxide thin film (WO3).
c film (hereinafter referred to as EC film) 4, photoconductive film 5 such as CdS film
, a transparent conductive film 6 which is a second transparent conductive film such as an ITO film,
Gadolinium iron (GdFe) thin film with electro-optic effect,
Thin films for magneto-optical recording such as terbium iron (ThFe) films (m
The agneto-optic films (hereinafter referred to as MO films) 7 are laminated in the above-mentioned order by vapor deposition or sputtering. Here, the MO film 7 is a perpendicularly magnetized film and has a film thickness that allows sufficient light transmission (for example, about 200 to 300 Å).
The thickness of the films other than the MO film 7 is approximately 0.5 μm.

Recording and reproduction of the above-mentioned two-layer optical memory 1 will be explained below. First, the first and second two layers are connected to the two-layer optical memory.
When recording two digital signals simultaneously in 2-bit parallel,
A first digital signal (as shown in FIG. 2A) is transmitted between the transparent conductive film 3 and the transparent conductive film 6 of the two-layer optical memory 1.
For example, the first digital signal whose time series is 0101...)
Apply a voltage V modulated to correspond to (for example, +V0 when the first digital signal is 0, -V0 when the first digital signal is 1, ±V0 = ±1 [V]), and A second digital signal (for example,
A magnetic field H modulated to correspond to a second digital signal whose time series is 0011... (for example, +H0 when the second digital signal is 0, -H0 when the second digital signal is 1)
, ±H0=±100 [Oe]), and then
) in a discrete time series as shown in FIG. A linearly polarized laser beam 8 is focused to a diameter of about 1 μm and irradiated with an objective lens (not shown) to a recording position (hereinafter simply referred to as recording position) specified by the two-dimensional coordinates of vertical X and horizontal Y on the surface of . At this time, since only the temperature at the recording position (1 μmφ) of the MO film 7 irradiated with the laser beam 3 increases,
The coercive force in this part decreases. As mentioned above, the MO film 7
Since a magnetic field H modulated by the first digital signal is applied to , only the recording position (1 μmφ) of the MO film 7 irradiated with the laser beam 8 is magnetized in the direction of the magnetic field H. . Further, since the MO film 7 has a thickness of about 200 to 300 Å, the laser beam 8 passes through the MO film 7 and the transparent conductive film 6 and irradiates the photoconductive film 5. At this time, conductivity occurs only at the recording position of 1 μmφ on the photoconductive film 5 that is irradiated with the laser beam 8. As mentioned above, since the voltage V modulated by the first digital signal is applied between the two transparent conductive films 3 and 6 placed at opposing positions,
1 μmφ in contact with the conductive part of the photoconductive film 5 of the EC film 4
A voltage V is applied to the recording position. Therefore, only the portion of the EC film 4 to which the voltage V is applied is colored or decolored.

Further, since the EC film 4 has a memory function, the colored/decolored state is maintained even if the voltage V is no longer applied.

As described above, two bits of the first and second digital signals are simultaneously recorded in parallel on the MO film 7 by the magnetic field H and in the EC film 4 by the voltage V.

Next, a description will be given of reproduction of two digital signals, first and second, recorded in parallel with 2 bits in a two-layer optical memory.

1st and 2nd bits recorded in parallel in 2-layer optical memory
To reproduce the two digital signals, similarly to the recording described above, a laser beam 8 of a constant light amount P (for example, P=P0) is transmitted through a polarizer in a discrete time series as shown in FIG. The two-dimensional coordinates of vertical X and horizontal Y on the surface of the MO film 7 of the two-layer optical memory 1 in which the first and second two digital signals are recorded in parallel in 2 bits by converting the laser beam 8 into a linearly polarized laser beam 8 1 by an objective lens (not shown) at the recording position specified by
Irradiation is focused on the order of μmφ. However, the voltage V applied during recording and the applied magnetic field H are kept at zero level. When the laser beam 8 passes through the MO film 7, its polarization plane is changed to a direction opposite to the direction of the magnetic field recorded in the MO film 7 due to the Faraday effect.

Further, when the laser beam 8 passes through the transparent conductive film 6, the photoconductive film 5, and the EC film 4, the amount of transmitted light of the laser light 8 is changed in accordance with the coloring/decolorization of the EC film 4.

Therefore, the laser beam 8 transmitted through the two-layer optical memory has M
The laser beam 8 is subjected to polarization plane modulation by the O film 7 and amplitude modulated by the EC film 4. This transmitted laser beam 8 is guided to a half mirror 11 through a lens 10, divided into two parts by the half mirror 11, and then passed through analyzers 12 and 13, which are rotated in opposite directions around the extinction position. The light is received by certain photodetectors 14 and 15.

The output terminals of the photodetectors 14 and 15 are connected to operational amplifiers 16 and 17 in order to calculate the sum and difference of output signals corresponding to the transmitted light received by the photodetectors 14 and 15. The output signal of the operational amplifier 16 which calculates and outputs the sum of the output signal of the photodetector 14 and the output signal of the photodetector 15 is the polarization of the transmitted laser beam 8 because the signals of the amplitude modulation components of the transmitted laser beam 8 cancel each other. The output signal of the photodetector 14 and the photodetector 15 are only plane modulation component signals, as shown in FIG. 3(A).
Since the signals of the polarization plane modulation components of the transmitted laser beam 8 cancel each other, the output signal of the operational amplifier 17 which calculates and outputs the difference between the output signal and the output signal of the transmitted laser beam 8 is only the signal of the amplitude modulation component of the transmitted laser beam 8, The time series becomes as shown in FIG. 3(B).

As described above, from the output terminal of the operational amplifier 16 to the MO
The second digital signal recorded on the film 7 (time series is 001
1...) is recorded on the EC film 4 from the pre-operation amplifier 17, and the first digital signal (first digital signal with time series 0101...) is obtained independently and simultaneously.

(Effects of the Invention) Since the present invention has the above-described configuration, the recording density is doubled, so high-density recording is possible, and two digital data can be stored and reproduced in parallel at the same time. There is no need to erase records, and since overlapping recording (writing) is possible, the time required for recording and reproduction is reduced, and it has the advantage of being suitable for high-speed recording and reproduction.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the structure and operation of an embodiment of a two-layer optical memory according to the present invention, and FIG. 2 is a diagram showing light, voltage, and magnetic fields applied to the two-layer optical memory shown in FIG. FIG. 3 is a diagram showing a time-series change in the signal output recorded in the two-layer optical memory shown in FIG. DESCRIPTION OF SYMBOLS 1... Two-layer optical memory, 2... Transparent substrate, 3, 6... Transparent conductive film, 4... EC film, 5... Photoconductive film, 7... MO
Film, 8... Laser light, 9... Polarizer, 10... Objective lens, 11... Half mirror, 12, 13... Analyzer, 14,
15...Photodetector, 16,17...Operation amplifier. Patent applicant: Ichiro Shinji, representative of Victor Japan Co., Ltd.

Claims (5)

[Claims] (1) a transparent substrate, a first transparent conductive film formed on the transparent substrate, and an electrochromic thin film for recording a first digital signal formed on the first transparent conductive film;
A photoconductive film formed on the electrochromic thin film, a second transparent conductive film formed on the photoconductive film, and a magneto-optical film for recording a second digital signal formed on the second transparent conductive film. A two-layer optical memory consisting of a recording thin film. (2) A two-layer optical memory according to claim 1, wherein each of the films is formed by sputtering. (3) A two-layer optical memory according to claim 1, wherein each of the films is formed by vapor deposition. (4) a transparent substrate, a first transparent conductive film formed on the transparent substrate, and an electrochromic thin film for recording a first digital signal formed on the first transparent conductive film;
A photoconductive film formed on the electrochromic thin film, a second transparent conductive film formed on the photoconductive film, and a magneto-optical film for recording a second digital signal formed on the second transparent conductive film. When irradiating linearly polarized laser light from the magneto-optical recording thin film side to the transparent substrate side in order to record the first and second digital signals in a two-layer optical memory consisting of a recording thin film, Recording the first digital signal on the electrochromic thin film by applying an electric field modulation signal corresponding to the first digital signal between the first transparent conductive film and the second transparent conductive film. and a two-layer optical memory in which the second digital signal is recorded on the magneto-optical recording thin film by applying a magnetic field modulation signal corresponding to the second digital signal to the magneto-optical recording thin film. recording method. (5) a transparent substrate, a first transparent conductive film formed on the transparent substrate, and an electrochromic thin film for recording a first digital signal formed on the first transparent conductive film;
A photoconductive film formed on the electrochromic thin film, a second transparent conductive film formed on the photoconductive film, and a magneto-optical film for recording a second digital signal formed on the second transparent conductive film. irradiating linearly polarized laser light from the magneto-optical recording thin film side to the transparent substrate side in order to reproduce the first and second digital signals recorded in a two-layer optical memory comprising a recording thin film; At this time, the transmitted light from the transparent substrate of the linearly polarized laser light irradiated to the magneto-optical recording thin film is divided into two, and the two transmitted lights are detected by two light receiving elements that receive the transmitted light through an analyzer. A reproducing method for a two-layer optical memory in which the first and second digital signals are independently and simultaneously reproduced by obtaining a sum signal and a difference signal.