JPS59142755A - Optical information storage device - Google Patents

Abstract

PURPOSE:To erase a recording bit completely on a recording medium by scanning mutually beams of a recording and a reproducing head on the area different in bit when the bits are erased. CONSTITUTION:The tracking mirror 30 of the reproducing head is supplied with a bias externally from a bias voltage generator 27 to scan its beam on a position a little bit off the center of a track outwardly. The recording head, on the other hand, scans the recording beam on the track according to a tracking signal from a buffer memory 24 while the direction of a magnetic field produced by a magnetic coil 19 is made opposite. At this time, the tracking signal is sent to the tracking mirror 20' of the recording head after being delayed through a delay circuit 28 by the time difference of the movement of the same bit between the reproducing and recording heads, and the recording beam scans on a position a little bit off the center of the track inwardly by a bias voltage generator 27'. Thus, the recording and reproducing heads are used at the same time to erase a recording signal widely.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information storage device, and more specifically,
The present invention relates to an optical information storage device capable of recording information on a recording medium using a light beam, reproducing the recorded information, and erasing the recorded information.

A typical example of such an optical information storage device is
An example is a magneto-optical disk device that uses a disk-shaped recording medium having a magnetic film. Information recording in this magneto-optical disk device is performed in the following process. The magnetic film on the recording medium is magnetized in advance with alignment in the perpendicular direction.

A light beam modulated according to information is irradiated onto this magnetic film from a recording section consisting of a laser light source, an imaging lens, etc. The temperature of the portion irradiated with the light beam increases due to the light energy, and when the temperature reaches the Curie point temperature (approximately 160° C.), the direction of magnetization becomes disordered. Next, when the position of the light beam moves to another part as the recording medium moves, the temperature decreases, and the magnetization direction is reversed from the surroundings by the surrounding magnetic flux and magnetized again. In this way, information is recorded on the magnetic film as a reversal of magnetization, forming a signal train.

On the other hand, during reading, a light beam oscillated from a semiconductor laser or the like in the reproducing section and polarized by a polarizer is irradiated onto the signal train formed on the magnetic film, and the magnetization direction of the irradiated part is followed by the magnetic hexagonal effect. It is reflected as optically rotated light.

This reflected light is separated from the incident light by a beam splitter or the like in the reproduction section, guided to a light receiving element through an analyzer, and information is reproduced by detecting the magnetization direction from the polarization direction.

This magneto-optical disk device is capable of high-density recording and has a recording density one to two orders of magnitude higher than that of a magnetic disk device. For example, a magneto-optical disk with a diameter of 300 mm can store approximately 10,000 pages of information on an A4-sized document with a resolution of 16 mm/mm.

FIG. 1 shows the positional relationship between a recording beam spot 1 and a recording bit 2 during information recording in this magneto-optical disk device. Here, the width Dw of the recording beam spot 1 in the scanning direction is about 1.3 to 1.8 μm, and the pitch P of the 20 rows of recording bits in the disk radial direction is 2 to 3 times the width Dw of the recording beam spot 1 in the scanning direction. That's about it. Incidentally, a feature of magneto-optical disk devices is that they can be read and re-recorded, and unnecessary information can be erased.

When erasing a recorded bit, the recording medium is rotated and a light beam is irradiated onto the recorded bit part while tracking the recorded bit string, and this part is raised to a single point, and the part of the recording medium other than the recorded bit is magnetized. This is done by cooling while applying a DC bias magnetic field in the same direction as the recording direction, in preparation for re-recording. A method of using a recording beam as a light beam during erasing is conventionally known. FIG. 2 shows the positional relationship between recording beam spot 1 and recording bit 2 during erasing. Here, the recording beam is controlled to scan the recording bit string, but perfect control is impossible;
If there is a deviation in tracking, 2/ , 2//
, 2"', which is not erased, is generated in recording bit 2, which has an adverse effect when information is re-recorded on this recording medium. In this way, the conventional method of using a recording beam to erase recorded bits In the magneto-optical disk device,
There was a drawback that the recorded bits could not be completely erased.

The present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to provide an optical information storage device that almost completely erases recorded bits without producing a residual signal.

The present invention achieves the above object by changing the width of the beam spot in the scanning direction during erasing to the width of the beam spot in the scanning direction during recording.

Hereinafter, the present invention will be explained based on examples. FIG. 3 is a side view showing an optical system of a reproducing head of a magneto-optical disk device according to an embodiment of the present invention. The light beam emitted from the semiconductor laser 11 is collimated by a collimator lens 12, then split into three beams by a grating 13, passes through a polarizer 14, is bent at a right angle by a tracking mirror 15, and is then bent at a right angle by a nof mirror 16. , passes through the objective lens 17 and focuses on the surface of the recording medium 18 as three spots. The positional relationship between the three spots and the recording bits is, for example, as shown in Figure 4.L is the center spot 1 on both sides of the recording bit, and 13 is the recording bit on the left and right, respectively. It is normal for it to start to take longer. The recording signal is reproduced and focused using one spot in the center, and the spots 113, 1 . , l is caused by the movement of the surface of the recording medium i8, etc., so that the center spot 12 becomes the recording bit 2.
2 (track), a differential output is obtained and used for tracking.

The three polarized beams reflected on the surface of the recording medium 180 are bent at right angles by the half mirror 16 and directed toward the light receiving element. While the central beam is used as an information readout signal, the cylindrical lens 20 changes the expansion and contraction of the beam due to defocusing into a change in shape, so this is detected by the 4-split detector 21 and the detected signal is The objective lens 17 is controlled to move up and down to keep it in focus. Each beam on both sides has a separate detector 22
a and 22b, and a tracking error signal is obtained as a differential output thereof.The angle of the tracking mirror 15 is changed using this signal to perform automatic tracking. 19 is a magnetic coil installed on the objective as 1st floor,
When erasing information, an external magnetic field is applied to the recorded bit portion.

The optical system of the recording head includes a light beam from a semiconductor laser 11 that is modulated according to information, and a cylindrical lens 2.
The optical system is approximately the same as the optical system of the reproducing head except that the polarizer immediately before the zero is unnecessary. Note that the tracking mirror 15 is held at a constant angle except when erasing recorded bits.

FIG. 5 is a perspective view schematically showing the above-mentioned magneto-optical disk device. The optical system 40 of the recording head and the optical system 40' of the reproducing head are arranged diametrically opposite each other on the recording medium 18, and are moved in the directions of arrows A and B (in the diametrical direction of the recording medium 18), respectively. Information is recorded and reproduced over the entire surface of the recording medium 18. In this way, since the optical system 40 of the recording head and the optical system 40' of the reproducing head are independent, information can be reproduced almost simultaneously with recording, preventing recording errors from occurring, and reproducing the reproduced information from another address. At the same time, editing processing such as page alignment can be performed while recording. Note that the light beam output of the reproducing head is set at a level that does not affect or erase recorded bits.

Erasing recorded bits is effectively performed by simultaneously using a recording head and a reproducing head. The output of the light beam of the reproducing head is set to the amount required for erasing, about 10 mW, and at the same time, the magnetic coil (19 in FIG. 3) is energized to form a magnetic field in the erasing direction. Then, the recording head continuously outputs a light beam, and the reproducing head erases the recorded bits while eating them. The scanning signal (tracking signal) at this time is sent to the recording head's tracking mirror (15 in Figure 3) with a predetermined time delay, so even a recording head without a tracking function can scan and erase recorded bits. Can be done.

FIG. 6 is a diagram showing the positional relationship between the light beam spot and the recorded bits when erasing the recording bits F mentioned above. 24 is the recording bit to be erased; 2 is the light beam spot from the reproducing head; 1. indicates the light beam spot from the recording head. Light beam spot 14 from the playback head
and σ) light beam spot from the recording head 1. are shown at the same recording bit 24 for ease of understanding, but
As can be seen from FIG. 5, they are actually located at positions shifted by half a circle on the recording medium 18. The light beam spot 14 scans the recording bit with its center at a position offset from the center line LL' of the recording bit by I)o toward the outer circumference, and the light beam spot 16 centers at a position shifted toward the inner circumference by Do. of course,
The light beam spot 14 forms a light beam on the inner peripheral side.

FIG. 7 is a block diagram showing an embodiment of the tracking control system of the present invention. Here, 21122a122b is the aforementioned four-division detector, detector, detector, 23 is a differential amplifier, 24 is a rough aperture memory, and 25 is a differential amplifier.
is a variable gain amplifier, 26 is a compensation amplifier, 27, 27'
are bias voltage generators for the reproducing head and recording head, respectively; 28 is a delay circuit; 29 and 29' are power amplifiers for the reproducing head and recording head, respectively; 30 and 30' are tracking mirrors for the reproducing head and recording head, respectively;
W1 to SW6 indicate switches. The table below shows the operations of switches SW1 to SW6 when reproducing and erasing information.

The operation of this block diagram will be explained below. During playback, only the switch SW1 is closed, and the detector 22a is closed.

22b is differentiated by the differential detector 23, and the obtained tracking signal is sent to the tracking mirror 30 of the reproducing head via the variable gain amplifier 25, the compensation amplifier 26, and the power amplifier 29, and the optical beam is tracked. is controlled so that the top is scanned correctly. When erasing, the operation is as follows. When an erasing command is issued, the switch SW is closed, and the tracking signal obtained in the same manner as during reproduction is temporarily stored in the paraphernalia memory 24. Subsequently, the optical beam output of the reproducing head is amplified (approximately 10 mW) until required for erasing, and the magnetic coil 19 is energized so as to form a magnetic field in the erasing direction (opposite to the recording direction). Switches SW1 to SW6 are switched to the front end (switched, and in this state, the buffer memory 2 that previously stored the tracking signal is
A tracking signal is read out from 4, and the track is scanned by the light beam of the recording/reproducing head in accordance with this tracking signal, and the signal is erased. At this time,
The tracking mirror 30 of the playback head shows the L of the track.
``l-'' The track is scanned by the recording beam according to the tracking signal from the buffer memory 24 by reversing the direction of the magnetic field formed. At this time, the tracking mirror 3 of the recording head
0', a tracking signal is sent with a delay by the delay circuit 28 by the time difference in which the same bit on the recording medium moves between the reproducing head and the recording head. Also, an external bias is applied to the tracking mirror 30' of the recording head by a bias voltage generator 27' in the opposite direction to that of the tracking mirror 30 of the reproducing head, so that the recording beam is shifted slightly toward the inner circumference of the center of the track. Scan the location.

By using the playback head and recording head simultaneously in this way,
As shown in FIG. 6, the recorded signal is erased over a wide range.

Although the above description has been made using a magneto-optical disk device as an example, the present invention is not limited to this, but can be applied to any optical information storage device that can record, reproduce, and erase information using a light beam. For example, materials such as TAAsGe undergo a phase transition depending on the energy of the irradiated light beam, and information is reversibly recorded by utilizing the change in reflectance between amorphous and crystalline materials.

When applying the present invention to such materials, an external magnetic field is not required, and the energy of the light beams emitted from the recording head and the reproducing head during erasing is switched to erasing energy, and as in the previous embodiment, two beams of light are generated. The beam is configured to scan different areas of recording bits. Furthermore, the present invention can be applied to optical information storage devices of various recording media, such as those that utilize the phase transition of vO3, and those that utilize a system of styrene oligomer and dye.

The optical information storage device of the present invention has separate recording heads and reproducing heads, and when erasing bits on a recording medium, the beams of these recording heads and reproducing heads are scanned in areas where the bits are different from each other so as to erase the erased area. Since bits are erased by widening the width of the bit, it is possible to eliminate residual erasing (residual signals) caused by poor tracking of the erasing beam, shaking of the device, etc. in conventional devices.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the positional system of a recording beam spot and recording bits when recording information in a magneto-optical disk device, and Figure 2 is a diagram showing the recording beam spot and recording bits when erasing information in a conventional magneto-optical disk device. 6 is a side view showing the optical system of the reproducing head of a magneto-optical disk device according to an embodiment of the present invention, and FIG. 4 is a diagram showing the positional relationship between three light beam spots and recording bits. Figure 5
FIG. 6 is a perspective view schematically showing a magneto-optical disk device according to an embodiment of the present invention, FIG. 6 is a diagram showing the positional relationship between a light beam spot and recording bits when erasing information, and FIG. 7 is a tracking control system. FIG. 2 is a block diagram showing one embodiment of the present invention. 40... Optical system of recording head, 40'... Optical system of reproducing head, 22a, 22b... Detector, 23... Differential amplifier, 24... Buffer memory, 25... Variable gain Amplifier, 26... Compensation amplifier, 28... Delay circuit, 27.27'... Bias voltage generator, 29, 29
'...Power amplifier, 30, 30'...Tracking mirror, SW1-S
W6...Switch.

Claims (1)

[Claims] An optical information storage device that is capable of recording information on a recording medium using a light beam, reproducing the recorded information, and erasing the recorded information. 1. An optical information storage device characterized in that when erasing a bit, the beams of the recording head and the reproducing head are scanned in regions of different bits, and the bit is erased by both beams.