JPS5982646A - Optomagnetic storage device - Google Patents

Abstract

PURPOSE:To prevent storage capacity from reduction due to the arrangement of a track address signal recording part by arranging two kinds of photo-detectors supplying magnetized information signals in reverse phase each other to a magneto optic head reading out recording information from a recording medium. CONSTITUTION:The magnetized information signals obtained from the photo- detectors 26, 27 for detecting memory information signals which are arranged on the reflection sides of respective polarized beam splitters 21, 22 have reverse phases each other. When an optical beam spot scans the track address signal recording part 3, the quantity of reflected light is changed in accordance with the existence of an already set-up pit. Since the changing signal is changed independently of the change of a degree of polarization the memory information signal detecting photodetectors 26, 27 detect signal change in the same phase each other. Therefore, a track address signal can be obtained by subtracting the detected signals of the memory information signal detecting photodetectors 26, 27 each other and adding the magnetized information signals without the influence of the track address signal.

Description

[Detailed Description of the Invention] Technical Field> The present invention uses a magnetic thin film as a storage medium, and records, reproduces, and records information by irradiating the storage medium with a light beam such as a laser beam.
The present invention relates to a magneto-optical storage device that performs erasing.

<Prior Art> In recent years, optical memory devices have attracted attention as high-density, large-capacity memory devices. The reason why this optical memory has a high density and a large capacity is that the bit, which is the unit of information recording, is determined only by the beam diameter of the light and can be made into a thick sound of about 1 μm. However, this imposes many limitations on the optical memory device. That is, in order to record information at a certain location or to reproduce information recorded at a certain location, the light beam must be positioned extremely accurately. In general, in read-only memory, address information can be stored in the recorded bits in advance, so the position of the light beam can be determined while reproducing the recorded information, but with additional recording memory or rewritable memory, address information can be stored in the recorded bits in advance. Since it is difficult to record the information at the same time, a method is adopted in which some guide signals and address information are fixedly stored in the memory board in advance. For example, FIG. 1 shows a partial perspective view of a conventional memory substrate. As shown in FIG. 1, a common method is to form uneven grooves on the substrate and record or reproduce information along these grooves. The uneven groove has a shape that is interrupted in a part of the circumferential direction, and this provides fixed bit information indicating the address of the groove. FIG. 2 is a partial plan view of the memory board. 1 is a disk substrate made of a glass material or a transparent polymer material such as PMMA, and 2 is engraved on the disk substrate 1 (depth is m-, where n is the refractive index of the disk n substrate, λ is the laser Wavelength of light 9 Optical beam guiding track, 3 is a track address signal recording part (the depth is the same as the above optical beam guiding trunk) intermittently carved on the disk substrate with ~.Original beam spot moves relatively in the circumferential direction within the light beam guiding track 2.Then, the light beam spot moves within the light beam guiding track 2.
When the light beam is about to come off, a phenomenon occurs in which the amount of reflected light of the light beam changes, and by detecting this phenomenon, the servo processing guides the light beam spot to the correct position.

Similarly, when the light beam spot traces the track address signal recording section 3, address information is obtained by reading changes in the amount of reflected light corresponding to the engraved pit rows.

This track address signal is necessary for information retrieval when the optical memory device is used as a storage device for a filing system. However, since the track address signal recording section 3 is provided, the usable area of the normal information recording section is reduced and the storage capacity is reduced.

Purpose of the present invention The present invention was made in order to prevent a decrease in storage capacity due to the arrangement of the track address signal recording section described above, and allows relatively easy signal processing without requiring any special treatment on the storage medium side. It is an object of the present invention to provide a new and useful magneto-optical storage device that makes it possible to record ordinary information even in a track address signal recording section by adopting this method.

<Embodiment> Hereinafter, an embodiment of a magneto-optical storage device according to the present invention will be described in detail with reference to the drawings.

FIG. 3 is a partial side sectional view of an example of a magneto-optical memory element according to the present invention. The magneto-optical storage element shown in the figure has a recording medium formed on the transparent substrate 3 shown in FIG. 1 is a disk substrate, 4 is a transparent SiO film, and 5 is GdDyFe, TbFe formed by sputtering, which becomes a recording medium.
An amorphous perpendicular magnetization film such as GdDyFe or GdTbDyFe, 6 a transparent 5i02 film, and 7 a Cu reflective film. Further, 8 is an adhesive layer, and 9 is a transparent substrate. The magneto-optical storage element shown in FIG. 3 above irradiates a portion of the amorphous perpendicularly magnetized film 5, which is a recording medium, with a laser beam to raise the temperature to around the Curie point temperature, and then changes the direction of magnetization of that portion using an external magnetic field. Recording is performed using a method of applying and reversing (thermomagnetic recording), and when reading recorded information, the amorphous perpendicularly magnetized film 5 is irradiated with coherent light, and the rotation of the plane of polarization due to the Kerr effect of the light is detected. By passing photons (polarizing beam splitter) or the like, changes in the magnetization state of the amorphous perpendicularly magnetized film 5 are detected as the intensity of light, and recorded information is read out. The SiO film 4 and SiO
The two films 6 and the Cu reflective film 7 are provided to increase the Kerr rotation angle by the amorphous perpendicularly magnetized film 5.

FIG. 4 is an explanatory diagram of the configuration of an example of the magneto-optic head according to the present invention, which records, reproduces, and erases information by irradiating the magneto-optical storage element of FIG. 3 with a laser beam.

lO is a laser device that can emit laser light with a predetermined intensity;
' + 1 is a collimating lens that converts the emitted laser beam into parallel light; 12 is a polarizer that transmits only polarized light in a predetermined direction; 13 is a polarizer that guides the reflected information light from the magneto-optical storage element 14 to the detection system side; A half prism having a function of increasing the magneto-optical rotation angle generated in response to a change in the magnetization state of the magneto-optical storage element 14, an objective lens that forms a minute spot on the 15-piece amorphous perpendicularly magnetized film 5, and 16 a reflected information beam. It is a half prism that divides the The half prism 16 has a reflectance and a transmittance of 1 for S waves and 1P waves.
It has optical characteristics such that the phase difference is close to 1 and the phase shift between the S wave and the P wave is small. 17.18 is a spot lens for rotating the polarization direction of the reflected information light in a predetermined direction and projecting a light beam in a predetermined size and shape onto each photodetector; 21.22 is an S wave, P A polarizing beam splitter that separates waves; 23 is a cylindrical lens; 24 is a composite element that detects changes in the relative distance between the objective lens 15 and the magneto-optical storage element 14 through a synergistic effect of the spot lens 20 and the cylindrical lens 23; It is a type photodetector.

Further, 25 is a composite element type photodetector that detects a relative positional shift between the optical beam guide track 2 carved on the magneto-optical storage element 14 and the optical spot. The relative error signals obtained by the composite element type photodetectors 24 and 25 are fed into a drive mechanism (not shown) as a feed bank, and the drive mechanism drives the objective lens 15 or the entire optical head.

By driving this objective lens I5 or the entire optical head, the light beam spot is shifted to the light beam guiding trunk 2.
The top is scanned with a predetermined size. 25 and 27 are photodetectors for detecting memory information signals.

Next, the change in the polarization state of the light beam after the light reflected by the magneto-optical storage element 14 passes through the no-tube beam 13 and reaches the memory information signal detection photodetectors 26 and 27 is shown in FIG. This will be explained using a vector diagram. In the figure, the direction of the arrow represents the deflection direction, and the length of the arrow represents the light intensity. Further, the polarization state of the laser beam incident on the magneto-optical memory element 14 is in the P direction. Figure (a) is...-Tubulism 1
The polarization state of the light transmitted through the node 6 is shown in FIG. 6, and FIG. In the figure, y + and M- indicate the polarization state of the reflected information light corresponding to the magnetization information in the magneto-optical memory element 14 .

However, in Tubulism I6, there is a relative phase shift of about 180° between the P wave and the S wave during reflection, so the reflected information light M %p on the transmission side (a) and the reflection side (b) −
The directions are different from each other.

It is a quartz or mica plate cut into rows and raised to a predetermined thickness, and can relatively shift the phase of polarized light having mutually orthogonal polarization planes by 180°. Therefore, it is possible to change only the orientation of the incident polarized light.

The polarized light passing through the azimuths of the 18 phase-lag axes in FIG.
The orientations A and B of the delay axis of Al1.18 are magneto-optical memory element 1
4 is set between 100 and 100 for the orientation of the incident polarized light.

With the following settings, two lights with mutually orthogonal polarization planes are
If the respective polarization axes of the polarizing beam splitter 2 and 22 are s and p in the figure, the polarizing beam splitter 2
1.22'f: The transmitted light is intensity-modulated according to the magnetization state of the magneto-optical memory element 14 (xl, x2 or Y11
Y2).

As described above, the photodetectors 2 for detecting memory information signals are installed on the reflective side of each of the polarizing beam splitters 21 and 22.
．． The magnetization information signals obtained by 6.27 have mutually opposite phases.

On the other hand, when the light beam spot scans the track address signal recording section 3, the amount of reflected light changes between locations where there are engraved pits and locations where there are no engraved pits. Since this change signal changes regardless of the change in the degree of polarization, the memory information signal detection photodetectors 26 and 27 obtain signal changes in the same phase.

As can be understood from the results below, by subtracting the detection signals of the memory information signal detection detectors 26 and 27 from each other, the magnetization information signal can be obtained without being influenced by the track address signal, and the above detection signal By adding the above to each other, it is possible to obtain a track address signal without being affected by the magnetization information signal. FIG. 6 shows a detector 26 and 27 for detecting memory information signals when magnetization information signals are recorded redundantly on the track address signal recording section 3.
FIG. 2 is an explanatory diagram schematically showing an output signal obtained in FIG. In the figure, 28 is a laser beam spot, 29 is a track address signal pit, and 30 magnetization information signal bits. or,
X is a signal waveform detected by the memory information signal detection detector 26, and Y is a signal waveform detected by the memory information signal detection detector 27. As shown in the same figure, x
10y is a signal waveform corresponding to a track address signal, and XY is a signal waveform corresponding to a magnetization information signal.

The magneto-optical storage device according to the present invention can have various configurations in addition to the above-described embodiments. For example, the structure of the optical beam guiding track or the track address signal recording section in the magneto-optical memory element I4 may be a structure that uses a change in reflectance, or a combination of both, in addition to the uneven groove shape. It's okay.

Effects> According to the present invention described above, normal information can be recorded even in the track address signal recording section using a relatively easy signal processing method, thereby preventing a reduction in the effective storage capacity and increasing the capacity of the optical memory device. This can greatly contribute to

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of a conventional memory board, FIG. 2 is a partial plan view of the memory board, FIG. 3 is a partial side sectional view of an example of a magneto-optical memory element according to the present invention, and FIG. FIG. 5 is a vector diagram showing changes in the polarization state of a light beam, and FIG. 6 is an explanation of an output signal obtained by a detector for detecting a memory information signal. It is a diagram. In the figure, ■: Disk substrate 2: Optical beam guiding trunk 3 Nidorak address signal recording section 4: SjO film 5: Amorphous perpendicular magnetization film 6: 5j02 film 7: Cu reflective film 8: Adhesive layer 9: Transparent substrate 10: Laser Equipment 1
1: Collimating lens 12: Polarizer 13: Half prism 14: Magneto-optical memory element 15: Objective lens 1
6: No Tsuta 23 Nijilintorical lens 24: Complex element type photodetector 25: Complex element type photodetector 26.2
7: Photodetector for detecting memory information signals Patent attorney
Aihiko Fukushi (and 2 others) Figure 2 Figure 3

Claims (1)

[Claims] 1. In a magneto-optical storage device that uses a magnetic film as a storage medium and records, reproduces, and erases information by irradiating the storage medium with a light beam such as a laser beam, a substrate of a magneto-optical storage element having the storage medium. By forming unevenness etc. on the information signal track and a guide track along the information signal track, and by forming unevenness etc. of a predetermined shape on the extension of the information signal track, an address signal is generated. A magneto-optical head that forms a fixedly stored address signal recording portion and reads recorded information of the storage medium is provided with two types of photodetectors that obtain magnetization information signals of mutually opposite phases, and the two types of photodetectors By subtracting the detection signal of the detector, 'Rq
A magneto-optical storage device comprising signal processing means for obtaining the address signal by adding the detection signals of the two types of photodetectors from the itt information signal.