JPH07192337A - Optical information recording and reproduing device - Google Patents

Abstract

PURPOSE:To always perform the information recording and reproducing in a stable manner even though the temperature of an optical recording medium rises by setting the intensity of reproducing light in accordance with temperature change of the optical information recording medium while it is reproducing the recorded information. CONSTITUTION:A CPU 1 sets data in DA converters 2 and 3 being used for recording and reproducing power and monitors the output of a preamplifier 7 through a peak holding circuit 8a, a bottom holding circuit 8b, a differential amplifier 8c and an AD converter 9 and detects the amplitudes of information signals. By monitoring the amplitudes of information signals, the CPU 1 adjusts the reproducing power to be its optimum condition and the reproduction of information is stably performed at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus, and more particularly to an optical information recording / reproducing apparatus for reproducing recorded information by utilizing magneto-optical interaction.

[0002]

2. Description of the Related Art Conventionally, there is known a method of recording / reproducing information on / from a disc-shaped information recording medium (hereinafter referred to as an optical disc) by utilizing magneto-optical interaction (polar Kerr effect). Among them, a medium structure as shown in FIG. 4 has been proposed as a super-resolution technique for realizing a recording density higher than the optical resolution of reproduction light.

FIG. 4A shows a sectional view of an optical disc which is an example of the super-resolution technique. The substrate 20 is usually a transparent material such as glass or polycarbonate, and an enhancement layer 21, a reproduction layer 22, a recording layer 2 are formed on the substrate 20.
3 and the protective layer 24 are laminated in this order. The arrow in the magnetic layer indicates the direction of magnetization in the film.

The recording layer 23 is made of, for example, TbFeCo or DyF.
With a film having a high perpendicular magnetic anisotropy such as eCo, recorded information is held depending on whether the magnetic domain of this layer is upward or downward. Reproduction layer 2
No. 2 is made of a material having a large saturation magnetization Ms and a small perpendicular magnetic anisotropy, and is an in-plane magnetization film at room temperature, but becomes a perpendicular magnetization film because the saturation magnetization Ms becomes small when the temperature reaches a predetermined temperature Tth.

When the information reproducing light is irradiated from the substrate side to the magnetic film having such a structure, a temperature gradient as shown in FIG.
When viewed from the side, as shown in FIG.
There will be an isotherm of th. Then, the reproduction layer 2
As described above, No. 2 does not contribute to the polar Kerr effect because it becomes an in-plane magnetized film at a temperature equal to or lower than the predetermined temperature Tth, and the information of the recording layer 23 is masked and invisible from the reproducing light side. On the other hand, the reproducing layer 22 becomes a perpendicularly magnetized film at a portion having a temperature equal to or higher than the predetermined temperature Tth. As a result, the recording layer 2 is formed only in the aperture portion which is smaller than the spot size.
Since the information of 3 is transferred, super-resolution is realized. In such a configuration, since an aperture can be formed on the rear side with respect to the direction in which the spot advances on the disc, RAD (Rear Ap
This is called "Error Detection".

FIG. 5 shows an FAD (Front Apert) which has an aperture on the front side with respect to the direction in which the spot advances.
An example of the configuration of the ure Detection) is shown. In this case, the reproducing layer 22 has weaker in-plane anisotropy than RAD, and at room temperature, the magnetic domain of the recording layer 23 is transferred to the reproducing layer 22 through the intermediate layer 25 by exchange coupling. The Curie temperature of the intermediate layer 25 is set to around 100 ° C,
When the medium is heated by the reproducing light and reaches the Curie temperature of the intermediate layer 25, the exchange coupling is broken, so that the magnetization direction of the reproducing layer 22 becomes in-plane. Therefore, when the Curie temperature of the intermediate layer 25 is set to the predetermined temperature Tth, the magnetic domain of the recording layer 23 is transferred only on the front side of the spot with the isothermal line of the predetermined temperature Tth shown in FIG. .

Another method for performing super-resolution is shown in FIG.
A configuration as shown in is also proposed. The reproducing layer 22 of FIG. 6A is a perpendicular magnetization film having a low coercive force, and by applying the initialization magnetic field Hb at room temperature, the magnetization is aligned in the direction of the initialization magnetic field regardless of the orientation of the recording layer 23. That is, recording layer 2
A domain wall is generated in a portion where the magnetization direction of 3 and the direction of the initialization magnetic field are opposite. With the magnetization of the reproducing layer 22 thus initialized, reproducing light is emitted while applying a reproducing magnetic field Hr in the direction opposite to the initializing magnetic field. At this time, in the low temperature portion of the reproducing light spot, the reproducing magnetic field is so adjusted that the coercive force of the reproducing layer 22 is larger than the energy for reversing the magnetization of the reproducing layer 22 due to the exchange force from the recording layer 23 and the reproducing magnetic field. Set the size of. That is, since the magnetization of the reproducing layer 22 is oriented in the direction of the initializing magnetic field in the low temperature portion, the magnetization of the recording layer 23 is masked and does not contribute to signal reproduction. However, when the temperature of the reproducing layer 22 is gradually increased by the irradiation of the reproducing light, the coercive force of the reproducing layer 22 is lowered, and the magnetization of the reproducing layer 22 is reversed in the portion where the domain wall exists due to the exchange force from the recording layer 23 and the reproducing magnetic field. That is, the magnetization of the recording layer 23 is transferred to the reproducing layer 22. In this way, it is possible to realize super-resolution in FIG. 6B in which only the portion in the spot where the temperature is equal to or higher than the predetermined temperature Tth contributes to signal reproduction.

In practice, an intermediate layer may be provided between the reproducing layer 22 and the recording layer 23 to control the domain wall energy, but the principle is the same as that shown in FIG.

[0009]

However, in the above-mentioned conventional example, the temperature distribution in the reproduction light spot contributes to the super-resolution, so that there are the following problems.

Normally, in an optical information recording / reproducing apparatus (hereinafter referred to as an optical disk drive), the internal temperature becomes higher by 10 to 20 ° C. than the external environment due to the internal heat generation. Therefore, there is a temperature difference immediately after the optical disc is mounted in the drive and when the disc temperature reaches the equilibrium state after a sufficient time. Then, even if the same reproducing power is applied to both, a difference occurs in the temperature distribution within the spot, so that the quality of the reproduced signal also differs. FIG. 7 shows the temperature distribution in the vicinity of the spot when scanning is performed with the same reproducing light intensity when the temperature reaches the equilibrium state immediately after the mounting of the disc and when the temperature reaches the equilibrium state by taking the case of RAD as an example. In the case of FIG. 7, the isotherm of the predetermined temperature Tth extends to around the center of the spot immediately after the disc is mounted (FIG. 7A), which is at the optimum level as the super-resolution effect. However, when reproducing with the same reproducing light intensity after the temperature of the disk is raised, the maximum temperature becomes high as shown in FIG. 7B, and the isotherm of the predetermined temperature Tth extends to the front side of the spot, resulting in the aperture. Becomes too large to play a small pit as soon as the disc is mounted. On the contrary, if the reproducing light intensity is set so that the optimum aperture is obtained after the disc temperature is raised, there is a problem that the temperature in the spot does not rise sufficiently at the temperature immediately after mounting and the aperture does not open.

[0011]

According to the optical information recording / reproducing apparatus of the present invention, the magnetic coupling state between a recording layer made of a perpendicularly magnetized film for magnetically retaining information and the recording layer changes with temperature. In an optical information recording / reproducing apparatus which reproduces recorded information by irradiating the optical information recording medium with reproduction light, using an optical information recording medium having at least a reproduction layer for reproducing the recorded information. The intensity of the reproduction light is set in accordance with the temperature change of the optical information recording medium in.

[0012]

According to the present invention, the intensity of the reproducing light is set according to the temperature change of the optical information recording medium during the reproduction of the recorded information, so that the information recording / reproducing is always stable. According to the present invention, for example, even after the optical information recording medium is mounted on the optical information recording / reproducing apparatus, even if the temperature of the optical information recording medium rises due to heat generation of the apparatus, the intensity of the reproducing light is changed accordingly. Then, the reproducing operation can be performed by adjusting the reproducing power to the optimum value.

It should be noted that the setting of the intensity of the reproduction light can be obtained by adjusting every predetermined time, or can be obtained based on the output from the temperature detector of the medium.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram for explaining the first embodiment of the present invention. In the figure, 1 is a CPU, 2 and 3 are DA converters, 4 is a switch, 5 is a laser driver circuit, 6 is an information recording / reproducing optical head, 7 is a preamplifier, 8a is a peak hold circuit, 8b is a bottom hold circuit, and 8c. Is a differential amplifier, 9 is an AD converter, 10 is an optical disk, 1
Reference numeral 1 is a disk mounting detector.

When performing the reproducing operation, the CPU 1 sets data in the reproducing power setting DA converter 3 according to the procedure described later, and the laser driver circuit 5 according to the set value.
To turn on the laser diode in the optical head 6. The light emitted from the laser diode is focused on the optical disc 10 by the optical head 6 and modulated according to the recorded information. The light received by the sensor in the optical head 6 is converted into a voltage by the preamplifier 7 and becomes an information signal. This signal is demodulated by a demodulation circuit (not shown), and the optical disc 10
Play the information recorded in.

When recording information on the disc, C
Data is set in the recording power setting DA converter 2 by the PU 1, and the DA converter 2 is set via the switch 4.
The input of the output of the above to the laser driver circuit 5 is controlled. A recording signal from a modulation circuit (not shown) is used as a control signal for the switch 4, and the laser is modulated according to the data of the recording signal to record on the optical disc 10.

The CPU 1 sets data in the DA converters 2 and 3 for recording power and reproduction power, and outputs the output of the preamplifier 7 to a peak hold circuit 8a, a bottom hold circuit 8b, a differential amplifier 8c and AD.
It is configured to monitor through the converter 9 and detect the amplitude of the information signal. That is, by monitoring the amplitude of the information signal, the CPU 1 can adjust to the optimum reproduction power each time.

FIG. 2 shows an example of the structure of the information area in a general optical disc. Each part of FIG. 2 has the following roles. (A) Lead-in Zone (lead-in area)
An area for performing focus control, tracking control pull-in, and servo adjustment for making the reproduction beam follow the information track on the optical disk. (B) Inner Test Zone (inner circumference test area) ... A test area in which the recording power is adjusted on the inner circumference side. (C) Inner Control Zone (inner peripheral control area): An area in which information about the disk is recorded, in which servo information, maximum reproduction power, erasing conditions, etc. are written. (D) Data Zone: An area effective for data storage. (E) Outer Control Zone (outer peripheral control area) ... An area on the outer peripheral side in which the same information as in (c) is written. (F) Outer Test Zone (peripheral test area) ... A test area for recording power adjustment on the outer peripheral side. (G) Lead-out Zone (buffer area on the outer peripheral side).

Of these, the test zones (b) and (f) are usually used only for testing the recording power. That is, in this area, reproduction is performed while varying the recording power in several steps (reproduction power is constant), and the recording power with the largest reproduction signal amplitude is set as the optimum recording power.

Therefore, in the present invention, when it is detected by the disk mounting detector 11 that a disk has been mounted, the focus control and tracking control are adjusted and then I
nner Test Zone and / or Oute
After the optimum recording power Pw at a certain reproduction power is obtained by r Test Zone, the signal recorded at Pw is reproduced at the reproduction power of several steps to obtain the reproduction power Pr having the highest signal level. Further, the CPU 1 operates the built-in or external timer circuit before or after the above operation.

At this time, since the reproduction power Pr is adjusted to the optimum value, stable information reproduction can be performed. After that, the playback state changes as the disc temperature approaches the temperature inside the drive over time.However, the time required for the disc temperature to rise and the time until the temperature reaches the equilibrium state cannot be understood to some extent. Therefore, by adjusting the reproduction power to the optimum value according to the same adjustment procedure several times every predetermined time from the disc mounting to the time when the thermal equilibrium state is reached, stable information reproduction can be always performed.

As described above, by adjusting the reproduction power several times according to the temperature rise after the disc is mounted,
The optimum super-resolution effect is always obtained, and it becomes possible to reproduce high-density pits exceeding the optical resolution capability of the spot.

Further, although the present embodiment has been described by taking the RAD as an example, it goes without saying that the same effect can be obtained also when reproducing a disc of the FAD type. Further, although the case where the in-plane magnetized film is used for the reproducing layer and the reproducing layer is the in-plane magnetized film in the mask portion has been described in the present embodiment, the present invention is not limited to such a film structure. it is obvious. Therefore, for example, as shown in FIG. 6, the direction of the magnetization of the reproducing layer made of the perpendicularly magnetized film is aligned in one direction by the initialization magnetic field to form a mask, and the magnetization of the recording layer is transferred and reproduced only in the high temperature portion. Even in such a case, it does not depart from the scope of the idea of performing information reproduction while changing the transfer state of magnetization depending on the temperature of the film, which is a feature of the present invention. That is, in the case of FIG. 6 as well, it is needless to say that the same effect can be obtained by adopting a configuration in which the reproduction power is changed according to the temperature rise after the disk is mounted as described in the present embodiment.

Since the enhance layer as shown in FIGS. 4 to 6 enhances the Kerr effect, the protective layer is used for protecting the magnetic layer and has no relation to the essence of the present invention. You can omit it. [Second Embodiment] Next, a second embodiment of the present invention will be described in detail with reference to FIG. However, members having the same functions as those shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. The member added to FIG. 1 is a disk temperature detector 12.

In this embodiment, the procedure for detecting the mounting of the disc and obtaining the optimum reproducing power is the same as that of the first embodiment, but the disc temperature detector 12 is used without using a timer.
The temperature of the disk immediately after mounting is taken in by the CPU 1. After that, the temperature of the disc can be detected by the disc temperature detector 12, so that the reproduction power can be adjusted every time the temperature rises by a predetermined amount, so that the information can be always reproduced under the optimum conditions. Further, in the present embodiment, the explanation has been made assuming that the temperature of the disc is detected. However, if it is difficult to detect the temperature of the disc itself, the temperature of the disc cartridge is detected and the same operation is performed to obtain substantially the same effect. To be [Third Embodiment] The present invention can also take another method by using the same configuration as that of FIG.

As in the second embodiment, the disc power is adjusted by detecting the mounting of the disc and the disc temperature at that time is monitored, but in the present embodiment, the reproducing power when the disc temperature rises is detected. Is calculated. As a premise of the calculation, it is assumed that the temperature rise of the disk due to the irradiation of the reproduction light is proportional to the reproduction light intensity. That is, the temperature of the disc when mounted is T0, and the optimum reproducing light intensity is Pr.
0, the maximum temperature of the medium in the spot is Tr, the disc temperature after t minutes is T1, and the optimum reproducing light intensity is Pr1, Pr1. (Tr-T0) = Pr0. (Tr-T1). Therefore, assuming that the maximum reached temperature Tr is known depending on the medium, it is possible to obtain the optimum reproduction power from the result of the reproduction power adjustment immediately after mounting and the disc temperature thereafter, and always set the reproduction power to the optimum state. If the maximum temperature Tr is unknown, Tr and Pr1 can be obtained simultaneously by performing the same adjustment as in the first embodiment immediately after mounting the disk and after increasing the predetermined temperature.

It is needless to say that the temperature of the disk cartridge may be used instead of the temperature of the disk itself in this embodiment as in the second embodiment.

[0028]

As described in detail above, according to the present invention, when the information is reproduced from the optical information recording medium in which the magnetic coupling state of the recording layer and the reproducing layer changes with temperature, the temperature change of the disc. Since the reproduction light intensity is set to the optimum value in accordance with the above, there is an effect that stable information recording / reproduction can be always realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining a first embodiment of the present invention.

FIG. 2 is a format diagram on a disc according to the present invention.

FIG. 3 is a configuration diagram for explaining a second embodiment of the present invention.

FIG. 4 is a principle diagram of a conventional RAD type disc.

FIG. 5 is a principle diagram of a conventional FAD type disc.

FIG. 6 is a principle diagram of a conventional RAD type disk using a perpendicular magnetization film.

FIG. 7 is a diagram illustrating a conventional problem.

[Explanation of symbols]

 1 CPU 2,3 D / A converter 4 Switch 5 Laser driver circuit 6 Optical head 7 Preamplifier 8 Peak detector 9 A / D converter 10 Optical disc 11 Disc mounting detector 12 Disc temperature detector

Claims (3)

[Claims] 1. An optical information recording medium comprising at least a recording layer made of a perpendicular magnetization film for magnetically retaining information and a reproducing layer in which a magnetic coupling state with the recording layer changes with temperature. In the optical information recording / reproducing apparatus for reproducing recorded information by irradiating the optical information recording medium with reproduction light, according to a temperature change of the optical information recording medium during reproduction of the recorded information, An optical information recording / reproducing apparatus characterized by setting the intensity of reproducing light. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the set value of the intensity of the reproduction light is obtained by adjusting every predetermined time. 3. The optical system according to claim 1, further comprising a detector for detecting the temperature of the optical information recording medium, wherein the intensity of the reproduction light is set based on the output from the detector. Information recording / reproducing apparatus.