JPH08147753A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE: To increase the recording density. CONSTITUTION: The converging beam of an optical head for erasing 1 has an elliptic shape and the major axis of the ellipse 27 is made parallel with the tangential direction 18 of a disk 11. The elliptic-shaped converging beam of a recording/reproducing optical head 2 is formed so that its major axcis 28 of the ellipse is parallel with the radial direction 19 of the disk 11. For this reason, the optical head for erasing 1 is arranged at right angle with the recording/reproducing optical head 2. Consequently, by making the major axis of the ellipse of the converging beam for erasure parallel with the tangential direction of the disk, an excellent erasing characteristic is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing device,
In particular, it relates to an erasable rewritable optical recording / reproducing apparatus for a magneto-optical medium or a phase change medium.

[0002]

2. Description of the Related Art In recent years, research on an external storage device having both high-speed accessibility of a magnetic disk for a computer and a large-capacity memory of an optical disk has been rapidly progressing. All of the next-generation disk devices are considered to be optical disk devices in view of the realization of high transfer rates and large memory capacities. In order to increase the density and increase the transfer rate of the optical disk device, it is necessary to reduce the beam focusing diameter and increase the erasing rate. For this, it is necessary to shorten the wavelength of the light source and increase the numerical aperture of the objective lens. In addition to this, it is possible to apply the super-resolution method by providing a light-shielding band in the collimated beam as a technique for further increasing the resolution. Is being considered.

Here, an example of a conventional optical recording / reproducing apparatus including a plurality of optical heads in which an erasing optical head and a recording / reproducing optical head are separated will be described with reference to FIG.

Two identical optical heads are arranged, one is an erasing optical head 1 dedicated to erasing, and the other is a recording / reproducing optical head 2 dedicated to recording / reproducing. The track address signal is written in the disk 11 in advance, and the synchronous operation of the optical heads 1 and 2 in the figure is performed based on the track address signal.

Next, the optical head will be described. The laser 3 is a semiconductor laser, and in the laser beam 29 emitted from the laser 3, the electric field direction 24 of the far-field (far-field) elliptical pattern 4 of the semiconductor laser is in a position parallel to the plane of the disk 11, and the far-field ( The long axis 10 of the far-field) elliptical pattern 4 is perpendicular to the plane of the disk 11. The far field (far field) is the aperture characteristic of the semiconductor laser. In general, a semiconductor laser has a very small cross-sectional area of a light emitting portion of several μm to several tens of μm.
A parallel linear beam of laser light cannot be obtained and the beam spreads. Therefore, with respect to the intensity distribution of the laser light on the light emitting surface (also called near-field elliptical pattern or near-field image), the intensity distribution of the laser light at a point sufficiently distant from the light emitting surface is shown. The laser light 29 from the laser 3 is collimated by the collimator lens 5, transmitted through the compound prism 6, polarized by the 45-degree mirror portion 7 in the direction perpendicular to the disk 11, and the objective lens 8 converts the laser light 29 into The beam is focused as an erase beam 9 on the disk 11.

The erase beam 9 on the disk 11 is also elliptical in shape, but the long axis 26 of the ellipse of the erase beam 9 is the long axis 10 of the far-field (far-field) elliptical pattern 4.
And are at a right angle. With this method, the optical MTF (Mod
Uration Transfer Function
n) increases, but causes crosstalk in the disk radial direction 19. The MTF is a modulation conversion function, and is considered to be a kind of transfer function in which the high frequency is attenuated in the output frequency response with respect to the input frequency response when the medium is regarded as a transmission line. The larger the value of this MTF, the better the frequency response of the output to the input,
The S / N of the reproduced signal is good.

The reflected light from the disk 11 is the objective lens 8
Is incident on the composite prism 6, is polarized at a right angle by the beam splitter 12, and is detected as a magneto-optical signal 15. Further, the reflected light from the disk 11 is polarized at a right angle by the beam splitter 13 and detected as a focus error detection and a tracking error signal 14.

Although one erase optical head 1 has been described above, the same operation is performed for the other recording / reproducing optical head 2 except that the major axis 28 of the ellipse of the recording / reproducing beam 17 is parallel to the disk radial direction 19. Both of the focused beams are optical MTs in the tangential direction 18 (linear velocity direction) of the disk.
F is increased, and the S / N of the reproduced signal is improved.

Next, FIG. 5 shows a diagram for explaining the operation principle of the conventional optical recording / reproducing apparatus with respect to the arrangement of the elliptical pattern of the focused beam on the disk. When the major axis 26 of the ellipse of the erase beam 9 is in the radial direction 19 of the disk, the erase beam 9
The erasing width of the recording / reproducing beam 17 does not increase in the disc tangential direction 18 (line bundle direction), and the recording / reproducing beam 17 has a focused beam pattern substantially equivalent to the subsequent recording / reproducing beam 17. The reason why the erasing width does not become large is that since the disk 11 of FIG. 4 rotates in the disk tangential direction 18 (recording direction in FIG. 5), the laser power per unit time cannot be large and the amount of heat generation is small. by.

Although the above is the case where there are two optical heads, erasing and recording / reproducing are performed in order to make the device compact.
Can be done with one optical head. For example, a configuration in which the focused beam has an elliptical shape is disclosed in Japanese Patent Laid-Open No. 61-208643 published on September 17, 1986 and September 1986.
As disclosed in Japanese Patent Application Laid-Open No. 61-210536, published on the 18th of March, they perform erasing and recording / reproducing with one optical head. Further, in Japanese Patent Laid-Open No. 3-212829 published on September 18, 1991, the same as the above-mentioned publication, but the focused beam is elliptical by a diffraction grating at the time of erasing.

[0011]

In the above-mentioned conventional optical recording / reproducing apparatus, both the erasing beam and the recording / reproducing beam have an elliptic major axis of the same shape in the direction perpendicular to the disc tangential direction (linear velocity direction). Therefore, the erasing width related to erasing cannot be made large, and a sufficient MTF cannot be obtained because it is the same width as the recording / reproducing width by the recording / reproducing beam.
On the contrary, if the erasing beam has a large erasing width, it enters into another track, which causes a tracking error.

An object of the present invention is to provide an optical recording / reproducing apparatus in which the major axis of the ellipse of the erasing beam is in the tangential direction (linear velocity direction) of the disk so that the erasing width is increased to ensure reliable erasing. To do.

[0013]

In the optical recording / reproducing apparatus of the present invention, a laser and a collimator lens for collimating laser light emitted from the laser and a compound prism for transmitting and splitting the laser light are provided. In an optical recording / reproducing apparatus having at least two optical heads for recording / reproducing and for erasing, including an objective lens for condensing the laser beam, the focused beam of the erasing optical head has an elliptical shape, and its ellipse major axis is So that it is parallel to the disc tangential direction,
The erasing optical head and the recording / reproducing optical head are arranged at a right angle so that the elliptical focused beam of the recording / reproducing optical head has its major axis parallel to the disk radial direction. Is characterized by.

Further, the electric field direction of the focused beam of the erasing optical head is set to be the tangential direction of the disk, and the electric field direction of the focused beam of the recording / reproducing optical head is set to be the disk radial direction. An optical recording / reproducing apparatus characterized by the above is obtained.

Further, the erasing laser beam and the recording / reproducing laser beam are combined by a compound prism, and an erasing beam parallel to the tangential direction of the disc and a right angle to the tangential direction of the disc are formed on the same track before and after. An optical recording / reproducing apparatus is obtained which is capable of individually controlling erasing and recording / reproducing by converging a recording / reproducing beam.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the optical recording / reproducing apparatus of the present invention, and FIG. 2 is a diagram for explaining the operating principle of the optical recording / reproducing apparatus of the present invention.

The optical recording / reproducing apparatus of this embodiment shown in FIG.
The erasing beam 16 of the erasing optical head 1 has two optical heads, an erasing optical head 1 for erasing data recorded on the disk 11 and a recording / reproducing optical head 2 for recording and reproducing data on the disk 11. The elliptical shape is such that its elliptical major axis 27 is parallel to the disc tangential direction 18 (linear velocity direction), and the elliptical recording / reproducing beam 17 of the recording / reproducing optical head 2 has its elliptical major axis 28 in the disc radial direction 19. The erasing optical head 1 and the recording / reproducing optical head 2 are arranged at right angles so that they are parallel to each other. Each of the erasing optical head 1 and the recording / reproducing optical head 2 has a laser 3
And the collimator lens 5 for collimating the laser light 29
A composite prism 6 that transmits and splits the laser light 29, and an objective lens 8 that focuses the laser light 29 on the disk 11. The above laser 3
For example, TE (Transversal El)
Electric) mode laser.

First, the erasing optical head 1 will be described.
The laser light 29 emitted from the laser 3 is emitted in the electric field direction 24 of the far-field (far field) elliptical pattern 4 of the semiconductor laser.
Is parallel to the plane of the disk 11, and the long axis 10 of the far-field (far field) elliptical pattern 4 is the disk 1.
It is perpendicular to the plane of 1. This laser light 29 is collimated by the collimator lens 5, passes through the compound prism 6, is polarized in the direction perpendicular to the disc 11 by the 45 ° mirror portion 7, and is condensed on the disc 11 by the objective lens 8. . Although the erasing beam 16 on the disk 11 is also elliptical in shape, the ellipse major axis 27 of the erasing beam 16 is perpendicular to the major axis 10 of the far-field (far field) ellipse pattern 4.

According to this method, the optical MTF deteriorates in the tangential direction 18 of the disk, that is, in the linear velocity direction, but the thermal transient response in the disk radial direction 19 can take a large amount of energy per unit time. The energy per unit area increases, and the erasing width increases in the track width direction due to thermal diffusion, so that wide erasing can be practically performed.

The reflected light from the disk 11 is the objective lens 8
After passing through, enters the composite prism 6, is polarized at right angles by the beam splitter 12, and is detected as a magneto-optical signal 15. Further, the reflected light from the disk 11 is polarized at a right angle by the beam splitter 13 and detected as a focus error detection and a tracking error signal 14.

FIG. 2 shows the shape of a focused beam when the erasing optical head 1 and the recording / reproducing head 2 are arranged at a right angle to the conventional arrangement of optical heads. The elliptical major axis 27 of the erase beam 16 focused on the middle track of the three tracks is parallel to the disc tangential direction 18, and the elliptical major axis 28 of the recording / reproducing beam 17 is parallel to the disc radial direction 19. is there. The intensity distributions of the erase beam 16 as far-field images are shown as a vertical transverse mode intensity distribution 31 and a horizontal transverse mode intensity distribution 32, respectively. An erasing beam 16 having an ellipse major axis in the disc tangential direction 18 is obtained by the erasing optical head 1 of FIG. 1, and a recording / reproducing beam 17 having an ellipse major axis in the disc radial direction 19 is recording / reproducing in FIG. This is due to the optical head 2. As a result, the erasing characteristics are better when the beam shape has an elliptical long axis in the disc tangential direction 18, and the bit forming mark subsequently formed by the recording / reproducing beam due to the thermal transient response is in the track direction. It is possible to obtain a large erase width. However, the erasing width needs to be controlled to a width that does not interfere with the adjacent tracks so as not to erase the already recorded data of other tracks.

Next, a case of an optical recording / reproducing apparatus using one optical head, here, as an example, a magneto-optical head will be described with reference to FIG.

In the laser 3 which has emitted the laser light 29 having a wavelength of 0.68 μm, an optical system having the same complex prism 23, collimator lens 5 and objective lens 8 as described above is constituted. The beam splitters 12 and 13 for detecting the magneto-optical signal 15, the focus error detection and the tracking error signal 14 are the same as the above optical head,
A wavelength of 0.83 other than the laser 3 having a wavelength of 0.68 μm
Laser 20 for emitting a laser beam 30 of μm and prism 2
2 and a third beam splitter 21 are newly provided. In the beam focused on the disk 11 by the objective lens 8, the major axis 27 of the erasing 0.83 μm elliptical beam 16 is in the disk tangential direction 18, and the major axis 28 of the recording / reproducing 0.68 μm elliptical beam 17 is the disk. It is arranged in the radial direction 19. With this optical head, you can erase with one optical head,
Recording and reproduction are possible at the same time.

[0025]

As described above, in the optical recording / reproducing apparatus of the present invention, the erasing optical head is arranged at a right angle to the recording / reproducing optical head, or the laser having another wavelength, the prism, and the third beam. By constructing an optical system additionally provided with a splitter, the major axis of the ellipse of the erasing beam can be made parallel to the tangential direction of the disk, so that good erasing characteristics can be obtained and recording density can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical recording / reproducing apparatus of the present invention.

FIG. 2 is a diagram for explaining the operation principle of the optical recording / reproducing apparatus of the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional optical recording / reproducing apparatus.

FIG. 5 is a diagram for explaining the operating principle of a conventional optical recording / reproducing apparatus.

[Explanation of symbols]

1 erasing optical head 2 recording / reproducing optical head 3 laser (0.68 μm) 4 far field (far field) elliptical pattern 5 collimating lens 6 compound prism 7 45 ° mirror part 8 objective lens 9 erasing beam 10 far field (far field) ellipse Pattern major axis 11 Discs 12 and 13 Beam splitter 14 Focus error detection and tracking error signal 15 Magneto-optical signal 16 Erase beam with ellipse major axis in disc tangential direction 17 Recording and reproducing beam with ellipse major axis in disc radial direction 18 Disc tangential direction 19 Disc radial direction 20 Laser (0.83 μm) 21 Beam splitter 22 Prism 23 Composite prism 24 Elliptical pattern Electric field direction 26 Elliptical major axis of erasing beam 9 27 Elliptic major axis of erasing beam 16 28 Recording / reproducing beam Oval Axis 29 laser beam (0.68 .mu.m) 30 laser beam (0.83 .mu.m) 31 vertical transverse mode intensity distribution 32 horizontal transverse mode intensity distribution

Claims (3)

[Claims] 1. A laser includes a collimator lens for collimating laser light emitted from the laser into parallel light, a compound prism for transmitting and splitting the laser light, and an objective lens for condensing the laser light. In an optical recording / reproducing apparatus having at least two optical heads for recording / reproducing and erasing, the focused beam of the erasing optical head is elliptical so that the major axis of the ellipse is parallel to the disc tangential direction. The erasing optical head and the recording / reproducing optical head are arranged at a right angle so that the elliptical focused beam of the optical head for use has an elliptic major axis parallel to the disk radial direction. Optical recording / reproducing device. 2. The erasing optical head is set so that the electric field direction of the focused beam is in the disc tangential direction, and the recording / reproducing optical head is set so that the electric field direction of the focused beam is in the disc radial direction. The optical recording / reproducing apparatus according to claim 1, wherein 3. An erasing beam parallel to the tangential direction of the disc and a rectifying beam perpendicular to the tangential direction of the disc are combined before and after on the same track by combining the erasing laser beam and the recording / reproducing laser beam with a compound prism. Focus the recording / playback beam,
An optical recording / reproducing apparatus characterized in that erasing and recording / reproducing can be independently controlled.