JPS6374148A - Optical memory device - Google Patents

Abstract

PURPOSE:To suppress the increase of a crosstalk due to the extension of the recording bit by setting the entire surface of the recording film of a magneto- optical disk in the same magnetizing direction as said recording bit and performing the recording/reproducing/erasing operations on a guide groove. CONSTITUTION:The layer light is projected on a groove 1 together with the application of a magnetic field Hw and the magnetizing direction of a heated part is coincident with the magnetizing direction of the area 2 between grooves 1. Thus the heated part serves as a recording bit. In an erasion mode a magnetic field adverse to the field Hw of the recording mode is applied to the groove 1 together with the irradiation of the laser light. Thus the magnetizing direction of the area on the groove 1 is set equal to that of the area 2. In such a case, the laser power and the applied magnetic field are reduced compared with those of the recording mode in order to avoid the change of the magnetizing direction of the area 2. Therefore, the magnetizing direction of the groove 1 is kept coincident with that of the area 2 despite the increase of the bit length. As a result, the substantial bit width has no change and the increase of the crosstalk is suppressed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to optical memory devices.

[Conventional technology]

A schematic diagram of a conventional magneto-optical memory disk is shown in FIG. 1 is a groove for recording information, and 2 is a groove space.

For grooves 1, data is erased before information is recorded, and pits are written during recording.The written pits are developed by thermal conduction, etc., and the width of the pits gradually increases from the initial stage of writing, as shown in Figure 3. Shows the growing shape. During erasing, in order to erase such pits, erase along groove 1 with an erase power higher than the laser beak power during writing, and erase the unerased portion between the grooves, resulting in the erase area shown in 4. becomes an area of random magnetization where erased states and written states coexist. By scanning the recording groove 1 with a reproduction beam, the pits are read and a reproduction signal is obtained.

[Problem that the invention seeks to solve]

However, as the length of the nine pits increases, the width of the pits also increases due to heat conduction, so there is a problem in that the p-stalk increases as the pit width increases.

Therefore, the present invention is intended to solve these problems.1 The purpose of the present invention is to not increase the ripple stalk even if the pit length becomes long.[Means for solving the problems] The optical memory device of the invention heats a recording film on a magneto-optical recording medium, which has a property that the rotation direction of polarized light changes depending on the direction of magnetization, by applying a magnetic field at the same time as local heating by condensing laser beam irradiation. In an optical memory device that aligns only the temperature-rising portion of the light with the direction of the applied magnetic field, performs recording or erasing depending on the direction of the magnetic field, and performs reproduction by detecting a change in the rotational direction of polarized light due to a change in the direction of magnetization of the recording film. After making the part (between the grooves) other than the grooves (on the grooves) where information is recorded, reproduced, and erased on the recording film in the same magnetization direction as the recording pits, recording, reproduction, and erasure are performed on the grooves. The feature is that during erasing, the laser power and applied magnetic field at the time of erasing are set at least below the laser power and applied magnetic field during recording so that the space between the grooves on the recording film does not go into the erased state. Features.

[Effect]

According to the above structure of the present invention, since the magnetization direction is aligned in the same direction as the written pit between the grooves, even if the pit width of the pit written on the groove becomes wide and protrudes between the grooves, the pit between the grooves is not a pit. Since the magnetization direction is the same, the pit shape is read as a pit with a constant width, and crosstalk due to widening of the pit width is completely suppressed. Furthermore, since it is only necessary to erase the pits on the grooves during erasing, it is only necessary to set the write laser power and applied magnetic field, and the following erase laser power and applied magnetic field. In order to prevent this from happening, if the recording surface is made to have the same state as the full writing pit at the initial stage when the disc is made, it is possible to record, play and erase from now on without having to write between the grooves. .

〔Example〕

A principle diagram illustrating the magnetization direction of the magneto-optical disk according to the present invention is shown in FIG. 2. Reference numeral 1 indicates the top of the groove where recording, reproduction, and erasing are performed, and 2 indicates the space between the grooves.

The arrows 9, 10, and 11 indicate the direction of magnetization of the recording film, and as shown in 10, the grooves are aligned in the same direction as the magnetization direction of the write pit. FIG. 2(α) shows a schematic diagram when recording pits are formed.

By condensing a laser beam onto groove 1 and simultaneously applying a magnetic field HW, the magnetization of the heated portion is aligned in the same direction as the magnetization direction between the grooves, and this portion is recognized as a recording pit. . A schematic diagram at the time of erasing is shown in Figure 2Cb)
A magnetic field Hm in a direction opposite to that during recording is applied to the recording film, and at the same time, a focused laser beam is irradiated to align the magnetization direction on the recording film in the direction 11 opposite to that between the grooves. At this time, in order to prevent the magnetization direction 10 between the grooves from becoming the erasing direction 11, the laser power and the applied magnetic field are set smaller than during recording.

Next, the pit shape will be explained. A schematic diagram showing the groove and pit shape is shown in FIG. They are all aligned. Therefore, the portion 6 that increases the cross F-reflection of the written pit 3 becomes the same as the direction 11 of magnetization between the grooves 2, and the actually recorded pit shape is 7 shown in FIG. 1(j). shape, and even if the pit length becomes longer, the actual width of the pit remains the same.
Therefore, an increase in crosstalk due to an increase in pit width can be completely suppressed. In the case of an actual pit length of 9 μm, when writing and reproducing were performed without aligning the grooves with the magnetization direction of the recorded pits, the crosstalk was -25aB, but when the grooves were aligned with the magnetization direction of the recording pits between the grooves. , the crosstalk was improved to -526B.

Next, during erasing, by performing erasing with a power of 83% of the recording laser power, it is possible to erase without erasing the portion where the rip-stalk increases and without erasing any unerased parts.

〔Effect of the invention〕

As described above, according to the present invention, the entire surface of the recording film of the optical memory disk is magnetized in the same direction as the recording pits before use, and the recording laser power is set to less than the erasing laser power. This makes it possible to completely suppress the increase in crosstalk caused by widening of the pit width without performing complex optical or electrical processing.

[Brief explanation of the drawing]

Fig. 1(α)...Schematic diagram showing the recording state of the present invention Fig. 1(b)...Schematic diagram showing the recording pit of the present invention Fig. 1(c)... ... Schematic diagram showing the erased state of the present invention Fig. 2 (α) ... Schematic diagram showing the magnetization direction during recording of the present invention Fig. 2<b> ... The present invention Schematic diagram showing the magnetization direction during erasing Figure 3 Schematic diagram showing the conventional recording/erasing state 1 Groove 2 where recording, reproduction, and erasing are performed...
...Groove interval 3 ...Pit 4 ...Erasure range 6 ...Part that is not recognized as an actual pit 7
・・・・・・Above the part written as the actual pit (Nose) (52) (Nose) Rub 20

Claims (2)

[Claims] (1) On a magneto-optical recording medium, which has the property that the direction of rotation of polarized light differs depending on the direction of magnetization, the local temperature is increased by irradiating a focused laser beam, and at the same time, the temperature on the recording film is increased by applying a magnetic field. In an optical memory device, the recording or erasing is performed by aligning only the portion of the magnetic field in the direction of the applied magnetic field, recording or erasing is performed depending on the direction of the magnetic field, and reading is performed by detecting a change in the rotational direction of polarized light due to a change in the direction of magnetization of the recording film. The feature is that the area (between the grooves) other than the grooves (on the grooves) where information is recorded, reproduced, and erased on the film is magnetized in the same direction as the recording pit, and then recording, reproduction, and erasing is performed on the grooves. Optical memory device. (2) The laser power and applied magnetic field during erasing are set at least lower than the laser power and applied magnetic field during recording so that the grooves on the recording film are not brought into an erased state during erasing. An optical memory device according to claim 1.