JPH0330138A - Magneto-optical disk device - Google Patents

Abstract

PURPOSE:To reduce a recording and reproduction error by mounting a stress sensor to a magneto-optical recording medium, and offering an optical recording condition especially at a high temperature thereby preventing deterioration in the quality of a reproducing signal. CONSTITUTION:A metallic strain gage with small size and high accuracy employing a thin resistance foil is used for a stress sensor 20, mounted on the surface of a magneto-optical recording medium base, and an output of the sensor is fed back to a laser drive circuit 11 through a spindle of a spindle motor 16 with a contact of a metallic hub 19 of the medium. When the medium 17 is placed at a high temperature, since the thermal conduction of the medium base is not uniform, a temperature gradient is caused in the base, a thermal stress is generated due to the temperature gradient to cause a strain to the base. Then the stress sensor 20 measures the strain and the temperature of the medium base is simply detected from the result of measurement, and when the temperature of the medium base is high, the light spot intensity at recording is weakened. Thus, the quality deterioration in the reproduction signal due to temperature and the recording reproduction error are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical disk device that magneto-optically records and reproduces information.

[Prior Art] Usually, the substrate of a magneto-optical recording medium used in a magneto-optical disk device is made of plastic such as polycarbonate. However, if the medium is left at high temperatures, a temperature gradient tends to form on the substrate, which tends to generate thermal stress. Conventional magneto-optical disk drives or magneto-optical recording media do not have a special stress measurement mechanism for measuring this stress.

Furthermore, the light spot intensity during recording on the magneto-optical recording medium was constant within the normally used ambient temperature range.

However, as disclosed in JP-A-63-187439, it has a defocus detecting means for detecting the relative position of the magneto-optical recording medium and the aperture lens, and the intensity of the light spot is changed according to the signal of the defocus detecting means. A magneto-optical recording system is known, but in this case as well, there is no particular mention of the temperature or the thermal stress of the medium substrate caused by the temperature.

[Problems and Objects to be Solved by the Invention] However, when conventional magneto-optical disk drives are used at high temperatures, the temperature of the medium also rises, creating a temperature gradient on the medium substrate. Thermal stress generated by this causes an increase in birefringence of the media substrate, resulting in a problem in that the quality of the reproduced signal tends to deteriorate. Furthermore, since the intensity of the optical spot during recording is constant within the temperature range normally used, there is also the problem that at high temperatures recording is performed outside of the optimal recording conditions, further degrading the quality of the reproduced signal.

The present invention is intended to solve these problems, and its purpose is to detect the temperature of the media substrate by measuring the strain caused by thermal stress on the media substrate, and also to detect the temperature range in which the magneto-optical disk device is used. The objective is to provide optimal recording conditions, especially at high temperatures, to prevent quality deterioration of reproduced signals and to reduce recording and reproduction errors.

[Means for Solving the Problems] A magneto-optical disk device of the present invention has the following features. (1) An optical head that detects recorded information on a magneto-optical recording medium using a light spot, an access mechanism that scans and drives the optical head in a seek direction with respect to the magneto-optical recording medium, and a housing that accommodates the magneto-optical recording medium. A magneto-optical disk device comprising at least a spindle motor to which a cartridge case is attached and rotated, and an external magnetic field generating means used for recording and erasing information, in which a stress sensor is attached to the magneto-optical recording medium; (2) The present invention is characterized in that the strain caused by thermal stress on the magneto-optical recording medium substrate is measured by the stress sensor, and the intensity of the light spot narrowed onto the magneto-optical recording medium is changed in accordance with the measurement result.

[Example] The present invention will be described in detail below based on examples.

FIG. 1 is a schematic configuration diagram showing an embodiment of a magneto-optical disk device of the present invention. This is the case when the transmitted light from the magneto-optical recording medium is detected and reproduced. First, let me explain the configuration 1
is an optical head, which includes a laser light source, an optical system for focusing a light spot onto a magneto-optical recording medium, a photodetector 9 for detecting transmitted light from the medium, a coil 8 for generating an external magnetic field, and an optical system. It includes a tracking actuator 6 and a focus actuator 7 that move the system minutely in the seek direction and the optical axis direction, respectively, with respect to the magneto-optical recording medium. Next, the functions of each part during recording, playback, or erasing will be explained. A laser beam 2 generated from a light source by a laser drive circuit 11 passes through a collimating lens 3, is reflected by a reflecting prism 4, and is focused by a focusing lens 5 onto a magneto-optical recording medium 17 as an optical beam. The magneto-optical recording medium is housed in a cartridge case 18, mounted on a spindle motor 16, and rotated. Information is recorded and erased by applying the magnetic field of a predetermined magnitude to the medium from the coil 8 by the coil drive circuit 15, and by irradiating the medium with the light spot. To reproduce the recorded information, a photodetector detects the light transmitted through the medium, and the reproduced signal processing circuit 14 extracts it as reproduced data. The focus control circuit 13 controls the focus shift of the light spot by moving a focus actuator. Similarly, tracking deviation is controlled by driving a tracking actuator by a tracking control circuit 12. Rough access to a track is performed by moving the optical head in the seek direction by the optical head drive motor 10.

20 is a stress sensor which is an important component for the present invention. This stress sensor uses a small, high-precision metal strain gauge made of thin resistance foil and is attached to the surface of the magneto-optical recording medium substrate. Although the shape of the sensor is arbitrary,
The thickness is such that it does not interfere with the rotation of the medium within the cartridge case, and the length is such that it covers the seek scanning area of the optical head. The output of the sensor is fed back to the laser drive circuit through the main shaft of the spindle motor using the metal hub portion 19 of the medium as a contact point.

Next, the relationship between the temperature of the medium substrate and strain due to thermal stress will be explained. When the media is exposed to high temperatures, temperature gradients occur within the substrate due to uneven heat conduction through the media substrate. This temperature gradient generates thermal stress, which causes distortion in the substrate. This medium substrate i; there is a certain relationship between the strain and thermal stress that occurs. Furthermore, it has been confirmed through experiments that the higher the ambient temperature, the more likely a temperature gradient will be formed on the media substrate, resulting in greater thermal stress. Therefore, measuring the strain on the media substrate uniquely determines the thermal stress, and if the thermal stress is known, the maximum temperature of the media substrate can be estimated. FIG. 2 shows an example of the relationship between the actual measurement results of strain produced on the media substrate and the maximum temperature of the media substrate.

Next 1: Stress measurement results and control of light spot intensity will be explained. A stress sensor can measure the strain caused by thermal stress on the media substrate. The measured strain results are fed back to the laser drive circuit, which controls the laser output power. At this time, the maximum temperature of the medium substrate is estimated from the measured strain results using FIG. 2, and if the temperature is plotted on the horizontal axis, the light spot intensity during recording is changed as shown in FIG. 3.

In other words, a negative slope is given so that the light spot intensity becomes smaller as the temperature increases. This slope is not fixed, but is set to 1 so that it can be set arbitrarily. At high temperatures, for example, if the area around the device is
If we consider the case of recording with the same light spot intensity as at room temperature at 0°C, since the temperature of the medium is already high, the light spot intensity will be excessive for the recording layer of the medium, and t
When recording on an s-body, recording pits interfere with adjacent bits due to thermal diffusion, which deteriorates the quality of reproduced signals. However, as mentioned above, if you detect the temperature of the media substrate and record by weakening the light spot intensity at high temperatures. Optimal recording conditions can be obtained even at high temperatures. When recording and reproducing were actually performed at high temperature using the magneto-optical disk device of the present invention, the C/N ratio of the reproduced signal was as shown in 30 in FIG. It was confirmed that the 4Jc/N ratio was improved by several dB at high temperatures compared to 31 when a conventional magneto-optical disk device was used.

Further, the stress sensor used in the magneto-optical disk device of the present invention is not limited to the metal strain gauge of the embodiment of the present invention, but may be any stress sensor as long as it is small, highly accurate, and thin.

Furthermore, it goes without saying that a structure incorporating a stress sensor like the magneto-optical disk device of the present invention can be applied to other information recording and reproducing devices that use laser light.

can be done. Therefore, quality deterioration of reproduced signals due to temperature is reduced, and recording/reproduction errors are reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic structural diagram showing an embodiment of the magneto-optical disk device of the present invention, FIG. 2 is a diagram showing the relationship between the temperature of the medium substrate and distortion due to thermal stress, and FIG. FIG. 4 is a diagram showing the change in light spot intensity during recording, and is a diagram showing the relationship between the temperature of the medium substrate and the C/N ratio in an embodiment of the present invention. [Effects of the Invention] As described above, according to the present invention, the stress sensor attached to the magneto-optical recording medium measures the strain caused by thermal stress on the media substrate, and the temperature of the media substrate can be easily detected based on the measurement results. I can do it. In addition, if the temperature of the media substrate is high, the light spot intensity during recording can be weakened, so that the optimum recording conditions can always be achieved within the temperature range in which the magneto-optical disk drive is used. Lens tracking actuator 8 9 10 11 12 13 1 4 15 16 17 18 19 2 0 3 0 Focus actuator Coil Photodetector Optical head drive motor Laser drive circuit Tracking control circuit Focus control circuit Playback signal processing circuit・Coil drive circuit ・Spindle motor ・Magneto-optical recording medium ・Cartridge case ・Metal hub portion ・Stress sensor ・Temperature characteristic curve of C/N ratio (present invention) ・Temperature characteristic curve of C/N ratio (conventional example) 2nd Illustration weight *A11 [Ib, I7l Distortion (gm ~ 冫銖Nephew clan's shifun (゛C) Figure 4 櫨体薊薊喊斥CC)

Claims (2)

[Claims] (1) An optical head that detects recorded information on a magneto-optical recording medium using a light spot, an access mechanism that scans and drives the optical head in a seek direction with respect to the magneto-optical recording medium, and a housing that accommodates the magneto-optical recording medium. A magneto-optical disk device comprising at least a spindle motor to which a cartridge case is attached and rotated, and an external magnetic field generating means used for recording and erasing information, characterized in that a stress sensor is attached to the magneto-optical recording medium. magneto-optical disk device. (2) The stress sensor measures strain caused by thermal stress on the magneto-optical recording medium substrate, and changes the intensity of the light spot focused on the magneto-optical recording medium in accordance with the measurement result. magneto-optical disk device.