JPH04311821A - Optical recording method and optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the crosstalk from an adjoining track and to improve the SN ratio of a reproducing signal by forming a track by a groove-shaped suggedness, forming an individual recording mark at the boundary, recording the information, scanning by the focusing light and reproducing. CONSTITUTION:A track is formed by a groove 101 shown by a projecting part and a land 102 shown by a recessed part and at a boundary 104, a recording mark 103 is formed. At the time of reproducing, the light emitted from a semiconductor laser 202 is reflected through a collimator lens 203 and a divided prism 206 by a total reflection mirror 204, and focused onto the recording surface of media 201 by an objective lens 205. The reflection light retrogrades, and is made incident on a detector 210 for controlling a focus and a detector 211 for controlling the position of the focus of the light on the track by the prism 206. A part of the reflection light is divided into polarization components orthogonal mutually through a polarization beam splitter 207 by the prism 206, made incident on light detectors 208 and 209 respectively, and by inputting the output into a differential amplifier, a reproducing signal 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 method and an optical recording/reproducing apparatus for optically recording or reproducing information.

0002

2. Description of the Related Art Optical recording and reproducing devices are characterized in that they can record a large amount of information and that the medium can be easily exchanged. An optical recording/reproducing device irradiates a medium with convergent light and reproduces changes in the intensity or phase of the reflected light (transmitted light) as a signal. Recording marks are formed on the medium by changing the shape, crystal structure, magnetization state, and molecular structure of the material of the reflective surface in order to change the intensity or phase of reflected light (transmitted light). Recording marks are arranged on a line, and the arrangement of recording marks is called a track.

Media are broadly classified into types that have grooves on the substrate and types that do not. The term "groove" may refer to a convex portion or a concave portion, but it usually refers to the side that has been processed. That is, in one context, either the convex portion or the concave portion is referred to as a groove. Types with grooves are controlled so that convergent light is scanned along the grooves using diffracted light from the grooves (hereinafter referred to as tracking control). There is an inter-groove recording method in which recording marks are placed in the area between the grooves. Further, in the type without grooves, recording marks are arranged in a mirror-like flat area, and tracking control is performed by control marks arranged intermittently.

0004

[Problems to be Solved by the Invention] However, as the distance between tracks (hereinafter referred to as track pitch) is reduced in order to increase the storage density of a medium, signal leakage from adjacent tracks (hereinafter referred to as crosstalk) occurs during playback. (referred to as talk) increases, leading to deterioration of the S/N ratio of the reproduced signal, resulting in a deterioration of the error rate. This is because the converged light has a certain size (hereinafter referred to as the spot diameter) on the recording surface, and the spot diameter is proportional to the wavelength of the light used, and the optical system used to converge it is proportional to the wavelength of the light used. It is inversely proportional to the aperture ratio. In other words,
If the spot diameter is made smaller, crosstalk will be reduced and recording with a smaller track pitch will be possible, which can be done by shortening the wavelength of the light or increasing the aperture ratio of the optical system. However, when it comes to the wavelength of the light source, the wavelength is 6
A highly efficient, high output, compact, economical, and coherent light source of 00 nm or less has not yet been realized. As for the aperture ratio, the depth of focus is inversely proportional to the square of the aperture ratio, so if the aperture ratio is increased, the depth of focus decreases rapidly, which impedes stable operation. Further, when the aperture ratio is increased, the working distance becomes smaller and the working distance becomes more sensitive to the tilt of the medium, so a value of around 0.06 is considered to be the limit. Therefore, there has been a desire for a recording method that can reduce crosstalk without changing the spot diameter and achieve higher recording density on the medium.

[0005] Therefore, an object of the present invention is to reduce crosstalk from adjacent tracks without changing the wavelength of light or the aperture ratio of the optical system, and to improve the S/N ratio of the reproduced signal, thereby making it possible to increase the density of the medium. The present invention provides an optical recording method and an optical recording/reproducing apparatus that do the following.

[0006]

[Means for Solving the Problems] The optical recording method of the present invention is an optical recording method in which a track is formed with groove-like unevenness on a substrate, and information is optically recorded and reproduced along the track. The optical recording and reproducing apparatus of the present invention is characterized in that information is recorded by forming individual recording marks at the boundary between the convex part of the track and the concave part of the track, and the optical recording/reproducing apparatus of the present invention An optical recording and reproducing apparatus that reproduces an optical recording medium recorded using a conventional recording method includes one or more light sources that emit light used for recording or reproducing, and that emits the light emitted from the light source onto the optical recording medium. one or more lenses for converging the converged light onto the boundary between the convex portion and the concave portion on the substrate; a focus control means for controlling the focal position of the converged light so as not to deviate from the surface of the optical recording medium; an optical position control means for controlling the position so that the optical recording medium scans; a detection means divided into two or more parts for detecting reflected light or transmitted light from the optical recording medium; It is characterized by comprising a reproduced signal generating means that selects and calculates outputs smaller than the number of divisions from among the outputs from each division to generate a reproduced signal.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the recording surface of a medium recorded by the optical recording method of the present invention. Here, FIG. 1(a) is a diagonal bird's-eye view of the recording surface, and FIG. 1(b) is a diagram of the recording surface viewed from directly above. The recording surface consists of groups (grooves) 101 represented by convex portions in the figure and lands 102 represented by concave portions. The characteristics of the optical recording method of the present invention are group 1
A recording mark 10 is placed on the boundary 104 between land 102 and land 102.
3 is formed. That is, a portion of one recording mark 103 is on the group 101 and a portion is on the land 102. In contrast, in conventional optical recording systems, recording marks are formed only on either groups or lands.

FIG. 2 shows a configuration diagram of an optical recording/reproducing apparatus for recording and reproducing data using the optical recording method of the present invention. This embodiment shows an example in which a magneto-optical recording medium is used as the recording medium. The light emitted radially from the semiconductor laser 202 is converted into parallel light by the collimator lens 203, transmitted through the splitting prism 206, and then the optical axis is adjusted to 9 by the total reflection mirror 204.
Can be bent by 0°. The light is then focused onto the recording surface of the rotating medium 201 by the objective lens 205. The light reflected on the recording surface passes through an objective lens 205, a total reflection mirror 204, and is separated by a splitting prism 206, and is separated by a focus control detector 210 and an optical position control detector 210 for controlling the position of the light focus on the track. The light enters the vessel 211. Further, a part of the reflected light is guided to a polarizing beam splitter 207 by a splitting prism 206. Polarizing beam splitter 207
The light is divided into mutually orthogonal polarization components and incident on photodetectors 208 and 209, respectively. Photodetector 208, 2
Since the light incident on the photodetector 209 has alternating current components of opposite polarity, a reproduced signal can be obtained by inputting the outputs of the photodetectors 208 and 209 to a differential amplifier. Here, the characteristics of the optical recording/reproducing apparatus of the present invention are that the photodetector 208,
209 is divided into two or more parts. FIG. 2 shows an example in which each is divided into two parts.

FIG. 3 is an explanatory diagram showing how a medium recorded using the optical recording method of the present invention is being reproduced. Convergent light 301 is incident on recording surface 306 . Here the convergent light 30
1 is drawn with a clear boundary, but it actually has a Gaussian distribution and has a spread. Here, while the recording marks recorded on the target track 302 are being reproduced, the reflected light 304 is modulated by the recording marks. In this case, the problem is crosstalk caused by recording marks recorded on the adjacent track 303. However, in the optical recording method of the present invention, the reflected light 305 from the adjacent track 303 forms an angle with the reflected light 304 from the target track 302, so the optical recording/reproducing apparatus of the present invention causes crosstalk between the reproduced signal and the reflected light 305. It becomes possible to separate the This will be explained using FIG. 4. FIG. 4 shows the signal reproducing section of the optical recording/reproducing apparatus of the present invention. A portion 401 of the reflected light from the recording surface is guided to a polarization beam splitter and divided into mutually orthogonal polarization components.
The light enters photodetectors 403, 404, 405, and 406, respectively. At this time, as explained in FIG. 3, since the reflected light from the target track and the reflected light from the adjacent track have an angle,
The reflected light from the target track is separated into a spot 411 and a reflected light spot 412 from an adjacent track. Therefore, the outputs of the photodetectors 403 and 404 have little crosstalk from adjacent tracks, so when these are input to the differential amplifier 407, a reproduced signal with little crosstalk is obtained at the output terminal 409. . Furthermore, when a track adjacent to the target track is reproduced as the target track, the reflected light spot of the target track appears on the photodetectors 405 and 406.
When these outputs are input to the differential amplifier 408, a reproduced signal is obtained from the output terminal 410. In this way, a single output with less crosstalk is obtained at the output end 414 by the switch 413 which selects either the output end 409 or 410 depending on the track to be reproduced.

Recording and reproducing experiments were conducted using the optical recording apparatus described above. The wavelength of the light source is 830 nm, the aperture ratio of the objective lens is 0.55, and the rotation speed of the medium is 1800 RP.
An experiment was conducted by recording a 1 MHz signal at a radius of 30 mm and a recording power of 7 mW. As the track pitch of the medium: 1.
When we experimented with 6 μm, 1.4 μm, and 1.2 μm, and measured the ratio of the crosstalk intensity from adjacent tracks to the signal intensity of the target track, it was -37 for each.
Values of dB, -33dB, and -29dB were obtained. This value is 5 dB to 7 dB lower than when recording using the conventional optical recording method. That is, in the optical recording method of the present invention, it is possible to obtain the same S/N ratio with a smaller track pitch than in the conventional optical recording method, so that it is possible to increase the recording density.

[0011]

As explained above, according to the optical recording method of the present invention and the optical recording/reproducing apparatus of the present invention, crosstalk from adjacent tracks is small when reproducing recorded information. , it is possible to record and reproduce at a smaller track pitch than conventional ones. In other words, it is possible to improve storage density without shortening the wavelength of the light source or increasing the aperture ratio of the objective lens, making it possible to provide an optical recording and reproducing device that can perform high-density recording and reproducing at low cost. . Moreover, since conventional manufacturing methods can be used as is for the manufacturing method of the medium, it is possible to supply low-cost media.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a recording surface of a medium recorded by the optical recording method of the present invention.

FIG. 2 is a configuration diagram of an optical recording/reproducing apparatus of the present invention.

FIG. 3 is an explanatory diagram showing how a medium recorded using the optical recording method of the present invention is being reproduced.

FIG. 4 is a signal reproducing section of the optical recording/reproducing apparatus of the present invention.

Claims (2)

[Claims] 1. An optical recording method in which a track is formed with groove-like unevenness on a substrate, and information is optically recorded and reproduced along the track, wherein a convex portion of the track and a concave portion of the track are provided. An optical recording method characterized in that information is recorded by forming individual recording marks on the boundary between the convex portion and the concave portion. 2. An optical recording and reproducing apparatus for reproducing an optical recording medium recorded by the optical recording method according to claim 1, comprising one or more light sources that emit light used for recording or reproduction; one or more lenses that converge the light emitted from the light source onto the optical recording medium; a focus control means that controls the focal position of the converged light so that it does not deviate from the optical recording medium; a light position control means for controlling the position so that the converged light scans the boundary between the convex part and the concave part; and a light position control means divided into two or more parts for detecting reflected light or transmitted light from the optical recording medium. It is characterized by comprising a detecting means, and a reproduced signal generating means that selects and calculates outputs from among the outputs from each division of the detecting means that are smaller than the number of divisions according to the position of the track to generate a reproduced signal. An optical recording and reproducing device.