JPH0697510B2 - Optical storage - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical storage device that stores information using laser light, and more particularly to a laser control system thereof.

<Prior Art> In recent years, an optical storage device has been widely studied as a memory device capable of high density, large capacity, and high speed access.

These are read-only memory for compact discs, video discs, etc., add-on memory for additional recording, recording and
It can be roughly divided into reversible memory that can be played and erased. a
As the dd on memory, there is a memory in which a Te alloy thin film, an organic film or the like is used as a storage medium, and fine bits or bubbles are formed on the medium by laser light irradiation to store information.
Further, as a reversible memory, a memory in which an amorphous magnetic thin film is used and the magnetization direction is finely inverted is stored.

By the way, in these add-on memory and reversible memory, generally, a method is used in which the medium temperature is locally raised by a laser beam that is minutely narrowed to deform or transform the medium. Therefore, the size and shape of the recorded bits change depending on the temperature distribution of the medium. For this reason, conventionally, in order to prevent S / N or bit errors from deteriorating when the ambient temperature of the storage device changes, the device temperature or ambient temperature is detected and the recording laser power or pulse length is changed. Measures were taken to keep the recording conditions constant.

This method is effective for the so-called rigid type in which the storage medium is fixed to the storage device, but when multiple storage media are exchanged and used by one device for the purpose of increasing the storage capacity or personal management of information. In this case, since the device temperature and the medium temperature do not necessarily match, there is a case where the recording condition is deviated and an inconvenience occurs.

<Purpose of the Invention> The present invention has been made in view of the conventional problems as described above, and by controlling the recording conditions, S /
This is to prevent the N, bit error rate, etc. from deteriorating.

<Example> Hereinafter, an example of an optical storage device according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration explanatory diagram of a magneto-optical storage device in the optical storage device according to the present invention.

Reference numeral 1 is a magnetic recording medium having a perpendicular magnetic anisotropy, which uses an amorphous alloy thin film of a rare earth metal and a transition metal as a recording material. Reference numeral 2 is a recording / reproducing / erasing optical head equipped with a laser device capable of emitting a laser beam of a predetermined intensity.

Reference numeral 3 is a magnetic field generator for applying a predetermined magnetic field to the magnetic recording medium 1, and 4 is a temperature sensor such as an infrared detector for detecting the temperature of the magnetic recording medium 1 in a non-contact manner. Reference numeral 5 is a motor that rotates the magnetic recording medium 1 at a predetermined speed, and 6 is a control device that corrects the output of the laser device based on the information from the temperature sensor 4.

Next, the importance and method of correcting the light output from the laser device will be described.

First, a recording method using an amorphous magnetic thin film will be described. As is well known, recording of information on an amorphous magnetic thin film is performed by a series of minute magnetization reversals. Then, in order to obtain this minute magnetization reversal region, the laser light narrowed down to a minute spot by the lens and the auxiliary magnetic field are used. FIG. 2 is a diagram qualitatively showing the relationship between the medium temperature and the coercive force of a GdTbFe material, which is an example of an amorphous magnetic thin film. As is clear from the figure, the holding force Hc decreases as the medium temperature rises.

FIGS. 3 (a), (b) and (c) show the magnetization change states of the medium before recording, during recording and after recording. The relationship between the medium temperature and the coercive force is as described above. Therefore, as shown in FIG. 3, a medium magnetized in one direction ((a) in FIG. 3) is laser-heated and the auxiliary magnetic field H _{B in the} opposite direction is applied. Is given ((b) in the figure),
A region having a coercive force of H _B or less is magnetized to be reversed, and recording or erasing is achieved ((c) in the same figure). The size of the magnetization reversal region is determined by the temperature rise distribution Tc of the medium and the size of the auxiliary magnetic field H _B , as can be easily inferred from the recording method. Although it depends on the size of the auxiliary magnetic field H _B , the type and composition of the amorphous magnetic thin film, the temperature level Tw of the magnetization reversal
Is generally set to 100-150 ° C.

Therefore, assuming that the optical storage device is used in an environment of 0 to 50 ° C., in order to achieve stable recording or erasing, the recording conditions should be corrected with respect to the ambient temperature and the medium temperature. Is essential. This point is not a phenomenon peculiar to the magneto-optical type, and even in the case of an optical storage device that performs bit formation, bubble formation, or bit formation by transformation, recording or erasing is performed by utilizing the temperature rise by laser light. The same thing can be said when doing.

As described above, the correction of the recording condition with respect to the temperature may be controlled based on the device temperature (environmental temperature), but especially when the recording medium is replaceable or a more stable condition is set. Should detect the temperature of the medium itself. Further, since this correction needs to be performed in real time (during device activity), in an optical storage device in which a medium moves, it is necessary to monitor and feed back the temperature in a non-contact manner.

An infrared detector is a temperature detecting element that realizes this. Among them, the pyroelectric detector is most suitable from the viewpoint of stability.

FIG. 4 is a block diagram of a control system for changing the laser power at the time of recording (or erasing) by an electric signal from a pyroelectric temperature detector. The control system is composed of a pyroelectric infrared detector 4, an environmental temperature measuring element 7, an arithmetic circuit 8 and a control device 6. Due to the characteristics of the pyroelectric detector, the medium temperature is the environmental temperature measuring element from the output of the detector 4. It is obtained by subtracting the output of 7 and feed-parking it.

Regarding the amount (coefficient) of changing the laser power,
It is calibrated so that the reaching temperature and distribution of the medium are almost constant.

<Effects of the Invention> According to the present invention described above, the electromagnetic wave radiated from the replaceable recording medium is detected and the temperature thereof is monitored, and the laser power is corrected accordingly. Stable recording or erasing can be achieved, and it is possible to prevent S / N deterioration and data error rate deterioration that occur due to differences in environmental temperature.

For the purpose of explaining the present invention, the pyroelectric infrared detector is taken as an example of the temperature detection element, but the detection element is not limited to this and other ones can be applied. Although the correction target is the intensity of the laser power, in digital recording where the recording bit length is important, a sufficiently useful result can be obtained even if the laser pulse length is changed. Further, in the magneto-optical device, the same effect can be obtained by controlling the strength of the auxiliary magnetic field.

Further, the present invention is effective when applied to a recordable optical memory, but is particularly effective in an erasable memory. This is because, in an erasable memory such as a magneto-optical medium, the medium temperature at the time of recording may differ greatly from that at the time of erasing, and the optimum conditions for the medium at that time may differ.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a magneto-optical storage device showing an embodiment of the present invention, FIG. 2 is a diagram qualitatively showing a relationship between a recording medium temperature and a holding force, and FIGS. 3 (a) and 3 (b). FIG. 4C is a diagram showing a magnetic change state of the medium before, during, and after recording, FIG.
The figure is a block diagram showing a control system when a pyroelectric temperature detector is used. 1 ... Magneto-optical recording medium, 2 ... Optical head, 3 ... Magnetic field generator, 4 ... Temperature sensor (infrared detector), 6
...... Control device, 7 ... Environmental temperature measuring element.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Ota, 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture, Japan Sharp Corporation (56) -131516 (JP, U)

Claims (1)

[Claims] 1. A replaceable optical storage device, wherein information is recorded or erased by heating the storage medium with a laser beam, the electromagnetic wave radiated by the storage medium is detected, and its temperature is measured. Detection means to monitor,
And an optical storage device comprising means for controlling laser power or laser pulse length based on information from the detecting means.