JP2573093B2 - Information recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium capable of automatically identifying a type of a medium in an information reading device.

(Prior art)

Generally, when reproducing information recorded on a recording medium such as an optical video disk, the recording medium is irradiated with laser light, and the reflected light or transmitted light is detected to read the information recorded on the recording medium. Things are going on.

Recently, when the linearly polarized light is reflected on the surface of a magnetic material or transmitted through the magnetic material, the phenomenon that the plane of polarization is rotated by the magnetic Kerr effect is applied, and the linearly polarized light is magnetically recorded on a magneto-optical recording medium. In order to increase the density of information recording and to make the magnetic Kerr effect remarkable, such magneto-optical recording media have perpendicular magnetic anisotropy, It is composed of a perpendicular magnetization film having an easy axis of magnetization in a perpendicular direction.

By the way, when information is recorded on the above-described magneto-optical recording medium, after all the recording areas of the medium are uniformly vertically magnetized in advance in the same direction, a specific area of the vertically magnetized area is irradiated with laser light. Then, the data is heated to the Curie temperature or the compensation temperature, and information is recorded by reversing the magnetization direction of the heated area.

When reading information recorded on a magneto-optical recording medium as described above, the medium is irradiated with laser light by utilizing the principle that a plane of polarization is rotated by a magnetic Kerr effect, and reflected light from the medium is reflected. And information reading is performed by detecting how much the polarization plane of the reflected light is rotated. Conventionally, an information reading apparatus for reading information recorded on a magneto-optical recording medium in this manner. Is configured as shown in FIG. 1, for example. Next, the information reading apparatus will be described.

In FIG. 1, (1) is a semiconductor laser, (2) is a polarizer that converts laser light from the laser (1) into linearly polarized light, and (3) transmits linearly polarized light from the polarizer (2). A first half mirror, (4) a convex lens for collecting linearly polarized light transmitted through the first half mirror (3), and (5) a magneto-optical recording medium having high coercive force and perpendicular magnetic anisotropy. Bismuth, gadolinium-iron, terbium-
It is composed of a magnetic thin film made of a rare earth-transition metal based amorphous alloy such as iron, gadolinium-terbium-iron, etc., and as shown by arrows in the figure, it is called above and below the magnetization direction of the magnetic thin film. Desired information is recorded in the form, linearly polarized light irradiated through the lens (4) is reflected by the medium (5), and the reflected light beam reaches the first half mirror (3) through the lens (4). And is reflected.

(6) is a second half mirror that transmits and refracts the reflected light beam from the medium (5) reflected by the first half mirror (3) and branches in two directions. (7a) and (7b) are polarizers ( The first and second analyzers set at the same angle on opposite sides with respect to the plane of polarization of the linearly polarized light according to 2), (8a),
(8b) is a first and a second photodetector which is a detection unit which detects light incident through both analyzers (7a) and (7b) and outputs an electric signal, and (9) is a differential type. This is a differential amplifier that is a reproduction circuit. Both input terminals (-) and (+) are connected to both photodetectors (8a) and (8b), and both photodetectors (8a) and (8b)
Signal is differentially amplified.

When the medium (5) is irradiated with linearly polarized light having a polarization plane in the direction of the solid arrow in FIG. 2, the magnetic Kerr effect causes the direction of magnetization when the linearly polarized light is reflected by the medium (5). Accordingly, the polarization plane is rotated with respect to the polarization plane of the linearly polarized light as indicated by the dashed arrow and the one-dot chain arrow in the figure, and for example, the polarization plane of the first analyzer (7a) in the figure is changed. The light is set so as to be perpendicular to the dashed arrow as shown by the two-dot chain line, and the light whose polarization plane rotates counterclockwise through the first analyzer (7a) as shown by the one-dot chain line in FIG. In the same manner, the second analyzer (7b) is set so as to transmit the light whose polarization plane rotates clockwise as shown by the broken line in FIG. When the reflected light beam has a polarization plane as shown by the one-dot chain line in FIG. Instead of passing through the second analyzer (7b), the light passes only through the first analyzer (7a) and reaches the first photodetector (8a). From the two photodetectors (8a) and (8b), for example, a logical " 1 "
And the signal "0" are input to both input terminals (-) and (+) of the differential amplifier (9), respectively.

On the other hand, when the reflected light beam from the medium (5) has a polarization plane as shown by a broken line in FIG.
The light passes through only the second analyzer (7b) without passing through the analyzer (7a), reaches the second photodetector (8b), and from the first and second photodetectors (8a) and (8b). Contrary to the counterclockwise case, signals of logic "0" and "1" are input to both input terminals (-) and (+) of the differential amplifier (9).

Next, both photodetectors (8a) by differential amplifier (9),
The respective signals from (8b) are operated, and the information recorded in the form of fluctuations in the upward and downward directions of the magnetization in the medium (5) is referred to as logic "1" and "0" by the differential amplifier (9). The digital signal is reproduced and output, and the information is read based on the reproduced digital signal.

By the way, the additional paying reader shown in FIG. 1 reads information recorded on a magneto-optical recording medium (5) reproduced by applying the magnetic Kerr effect, and the information is recorded in the form of uneven pits. When trying to read and read an optically reproduced optical recording medium such as a general video disk or a recording / reproducing disk of a compact disk player by the above-described apparatus shown in FIG. 1, the photodetectors (8a), ( 8b) cannot detect the change in the amount of light reflected from the medium (5) or the change in the amount of return light due to diffraction, and therefore the differential amplifier (9)
No signal is output from the device, and it is impossible to reproduce the recorded information, and it is necessary to prepare an information reading device according to the type of recording medium to be reproduced, which is very inconvenient and expensive. There is.

[Object of the invention]

The present invention has been made in consideration of the above points, and has as its object to provide a magneto-optical recording medium and an information recording medium capable of reading information recorded on the optical recording medium by one information reading device. Aim.

[Configuration of the invention]

According to the present invention, in an information recording medium provided with a magnetic recording layer made of a magnetic thin film having perpendicular magnetic anisotropy on a substrate, a signal indicating that the medium is a magneto-optical recording medium is recorded in at least a part of the information recording medium in advance. An information recording medium characterized by being recorded.

〔The invention's effect〕

Therefore, according to the information recording medium of the present invention, the operation of the information reading device can be controlled using the signal recorded in advance depending on whether the recording medium is a magneto-optical recording medium.

〔Example〕

Next, the present invention will be described in detail with reference to FIGS.

 First, FIG. 3 showing one embodiment will be described.

In the figure, the same symbols as those in FIG. 1 indicate the same parts, and the difference from FIG. 1 is that a discrimination signal indicating that the medium is a magneto-optical recording medium is recorded at the recording start position of the medium (5), Non-differential regeneration circuit adder (10) to dynamic amplifier (9)
The differential amplifier (9) for reproducing the magneto-optical recording medium reproduced by the magnetic Kerr effect and the dual photodetectors (8a), (8b) and the dual photodetectors (8a), (8b) And a connection portion (11) for selectively connecting the adder (10) for reproducing a magneto-optical medium such as a video disk to be optically reproduced. The differential amplifier (9) detects the discrimination signal. Output a command signal to the connection section (11) when both photodetectors (8a)
Command unit (12) for connecting (8b) and differential amplifier (9)
Is provided.

When reproducing the magneto-optical recording medium (5) and reading the recorded information, the discrimination signal recorded on the medium (5) is reproduced prior to the information at the start of the reproduction, and the command section (12) connects the connection section ( The command signal is output to 11) and the connection (11)
Thus, the differential amplifier (9) is connected to the two photodetectors (8a) and (8b), and the recorded information on the medium (5) is reproduced and read by the same operation as in the case of FIG.

Next, when reading recorded information by reproducing an optical recording medium such as a video disk or a recording / reproducing disk of a compact disk player, a signal similar to the discrimination signal is not recorded on these optical recording media. Command part (1
No command signal is output from 2).
The adder (10) is connected to the two photodetectors (8a) and (8b) by 1), and the information recorded on the optical recording medium is reproduced and read.

Therefore, according to the above embodiment, the information recorded on the magneto-optical recording medium (5) and the optical recording medium can be read by one information reading apparatus, and an information reading apparatus with excellent functions can be provided. .

Next, FIG. 4 showing another embodiment will be described.

In FIG. 4, the same symbols as those in FIG. 3 indicate the same parts, and the difference from FIG. 3 is that the discrimination signal indicating that the medium is a magneto-optical recording medium is not recorded on the magneto-optical recording medium (5). Manual switching instruction unit (13) including a changeover switch for outputting a connection switching instruction signal to the connection unit (11) instead of the command unit (12)
Is provided.

Therefore, according to the embodiment, only the switch of the indicator (13) is switched in accordance with the type of the medium to be reproduced, and the two detectors (8a) and (8b) and the differential amplifier are connected by the connector (11). (9) or the adder (10) can be selectively connected, and the information recorded on the magneto-optical recording medium and the optical recording medium can be read by one information reading device.

As shown in FIG. 5, an address is recorded in a specific area (14) of the recording area of one magneto-optical recording medium (5) by an uneven signal pit, and the remaining area (15) is magnetized. Even if information is recorded in the vertical direction of the information, the information based on the address of the signal pit and the magnetization direction are recorded at the recording start position and the recording end position of the area (14), respectively. Is stored in advance, and like the command unit (12),
By providing a command unit that detects the determination signal and outputs a command signal to the connection unit (11), the present invention can be similarly implemented.

[Brief description of the drawings]

FIG. 1 is a block diagram of a conventional information reading apparatus, FIG. 2 is an operation explanatory view showing the relationship between the planes of polarization of incident light and reflected light on the recording medium of FIG. 1, and FIGS. FIG. 3 shows a block diagram of one embodiment, FIG. 4 shows a block diagram of another embodiment, and FIG.
The figure is a front view of a recording medium according to still another embodiment. (1) laser, (5) magneto-optical recording medium, (8
a), (8b) ... photodetector, (9) ... differential amplifier, (1
0) Adder, (11) Connection.

Claims (1)

(57) [Claims] An information recording medium in which a substrate is provided with a magnetic recording layer made of a magnetic thin film having perpendicular magnetic anisotropy,
An information recording medium characterized in that a signal indicating that the medium is a magneto-optical recording medium is recorded in advance on at least a part of the information recording medium.