JPH07296416A - Optical disk and optical disk recording and reproducing device - Google Patents

Abstract

PURPOSE:To substantially increase the recording density of an optical disk without changing a laser wavelength and the numerical aperture of an objective lens by recording fresh information in land parts in addition to the information recorded as pits. CONSTITUTION:The spectral rays respectively detected by photodetecting elements SE 11, SEM 1, SE 31, SEM 2, SEM 3 of a photodetector SE are used in the following manner: A focus error signal is formed in accordance with the output signal of the element SEM 1. A bit reproducing signal is formed in accordance with the sum of the output signals of the elements SEM 2, SEM 3. A change over as to whether the information is reproduced in accordance with the bit reproducing signal or the information is reproduced in accordance with a magneto-optical reproduction signal is controlled by a system controller. A tracking error signal is formed from the difference between the elements SE 11 and SE 31. The signal is required to be inverted its polarity according to the case the pit parts are reproduced and the case the land parts are recorded/reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc having an increased recording density and an apparatus for recording / reproducing information on the optical disc.

[0002]

2. Description of the Related Art There are read-only optical disks and rewritable optical disks. The former is a compact disc (C
It is a disc in which information is recorded as pits (holes) as in D). The latter is to change the direction of magnetization of a perpendicular magnetization film formed on the surface of the disk like a magneto-optical disk (MO) in correspondence with "0" or "1" of information,
It is a disc that can record / reproduce information. Examples of such a magneto-optical disc include a rewritable mini-disc (MD) and a 3.5-inch standard magneto-optical disc (M which is a recording medium of computer data and has a capacity of 100 MB or more).
O) In addition to the magneto-optical disk, the rewritable disk includes, for example, a phase change disk.

In a rewritable mini disc (MD) for recording / reproducing music information, a perpendicular magnetization film is formed over the entire area, and a pre-groove for tracking is formed, and at the same time, the innermost part is formed. Management information is recorded as pits on the periphery.

[0004]

There is a demand to increase the recording density of an optical disc. As a method of increasing the recording density, there are a method of shortening the wavelength of laser light and a method of increasing the numerical aperture NA of the objective lens. The former requires improvement of the semiconductor laser, and the latter requires improvement in mechanical precision of the optical system of the optical pickup. That is, both require significant changes. Further, when recording information on a magneto-optical disk, it is necessary to switch the laser light output to a high power, but it is not possible to stably output a laser with a short wavelength at a high power for a long time. Have difficulty.

There is a demand for enabling personal information to be newly added and recorded on an already recorded disc. For example, if you want to record your score on a disc of game software, record your own voice on a disc of music software, or personally rewrite information on a disc such as a dictionary or database. For example, when you want to record. Although a write-once disc is available as a disc having such a function, the write-once disc has a problem that information cannot be rewritten.

An object of the present invention is to increase the recording density of an optical disk without changing the laser wavelength or the numerical aperture NA of the objective lens. In addition, on the recorded optical disc,
The purpose is to be able to record new information.
Further, the purpose is to be able to rewrite the recorded information.

[0007]

According to a first aspect of the present invention, there is provided an optical disc in which information is recorded as pits on a disc surface and a rewritable recording film of information is formed at least in a land portion. According to the second aspect of the present invention, in the mode for reproducing information, a laser beam of low power is applied to the disk and the information is reproduced based on the reflected light to write the information. An optical disc recording / reproducing apparatus for irradiating the disc with the light to set the state of the recording film to a state corresponding to the information, and a pit reproducing mode for reproducing information recorded as pits and a state of the recording film. In the pit reproducing mode, there is a mode specifying means for specifying either the recording film reproducing mode for reproducing the information recorded as the recording film or the recording film writing mode for writing the information as the state of the recording film. An optical disk recording / reproducing apparatus is provided with polarity switching means for switching the polarity of tracking control so that the pit portion is tracked and the land portion is tracked in the recording film reproducing mode or the recording film writing mode. According to a third aspect of the present invention, an optical disk recording in which a low power laser beam is applied to a disk in a mode for reproducing information and a high power laser beam is applied in a mode for writing information. A reproducing apparatus, a pit reproducing mode for reproducing information recorded as pits, a recording film for reproducing recorded information as a magnetization direction, and a recording film for writing information as a magnetization direction. A mode designating means for designating one of the writing modes,
Tracking control means for controlling tracking by the three-spot system and tracking control so that the pit portion is tracked in the pit reproducing mode and the land portion is tracked in the recording film reproducing mode or the recording film writing mode. In the pit reproduction mode, a signal corresponding to the intensity of the reflected light of the main spot is processed as a reproduction signal, and in the recording film reproduction mode, the rotation angle of the polarization plane of the reflected light of the main spot is changed. Reproduction signal processing means for processing a corresponding signal as a reproduction signal, and input information processing for processing the input information in the recording film writing mode to generate a magnetic field modulation signal and giving the magnetic field modulation signal to the drive circuit of the magnetic head. And an optical disc recording / reproducing apparatus including the means.

[0008]

In the optical disc of the first aspect, the rewritable recording film formed on the land portion is used to newly record and reproduce information. In the apparatus of claim 2, the mode is
One of the pit reproduction mode / recording film reproduction mode / recording film writing mode is specified by the mode specifying means. In the pit reproduction mode, low-power laser light is output, the pit portion is tracked, and information is reproduced based on the pit reflection light. In the recording film reproducing mode, low-power laser light is output, the land portion is tracked, and information is reproduced based on the reflected light from the land portion. In the recording film writing mode, laser light of high power is output, the land portion is tracked, and the input information is written in the land portion. In the device of the third aspect, writing of information to the land portion is performed by the magneto-optical magnetic field modulation method. Further, the reading of information from the land portion is performed based on the signal corresponding to the rotation angle of the polarization plane of the reflected light.

[0009]

EXAMPLES Examples of the present invention will be described below. FIG. 1A is an enlarged schematic view showing a part of the information recording surface of the optical disc of the embodiment. Information is recorded in advance on the illustrated optical disk as pits (indicated by an ellipse in the drawing). Information newly input by the user is recorded on the land portion between the pit portions by the magneto-optical method. In the figure, the pit portion and the land portion are separated by a thin broken line. When reproducing the pit part, the laser spot is irradiated as shown by the solid line in the figure, while when recording / reproducing at the land part, as shown by the chain double-dashed line in the figure.
The spot is illuminated. The laser spot LBM (LB
M ') indicates the main spot when tracking with the 3-spot method, and laser spots LB1 (LB1'), LB3 (LB3 ')
Indicates a side spot that precedes in time and a side spot that follows in time.

The laser spot of the three-spot system is
The information recording surface of the optical disc D is irradiated by the optical system of FIG. That is, the laser beam output from the semiconductor laser LD is split into three beams by a grating (diffraction grating) 51, and then collimated by a collimator lens 52 to be a beam. The light passes through the splitter 53, is condensed by the objective lens 54, and is irradiated onto the optical disk surface as described above. Further, each spot irradiated on the information recording surface of the optical disc D is reflected by the information recording surface, collimated by the objective lens 54, and then reflected by the beam splitter 53 to the Wollaston prism 55. Incident, the Wollaston prism
After being separated into 3 beams at 55, collimator lens 56
Then, the light is focused by the cylindrical lens 57 and reaches the photodetector SE.

The photodetector SE is composed of five photodetector elements SE11 and SEM.
1, SE31, SEM2, and SEM3 are integrated sensors with the arrangement of FIG. Here, the photo-detecting element SE11 is used to disperse the light in the center of the sub-spot LB1 (the center beam among the three beams dispersed by the Wollaston prism 55, and so on).
To detect. In addition, the photodetector SEM1 is the main spot
Detect the spectroscopic LBM1 in the center of the LBM. In addition, the photodetector SE
31 detects the spectral LB31 in the center of the sub-spot LB3.
On the other hand, the photodetectors SEM2 and SEM3 are the main spot LB
This element detects the spectroscopic LBM2 and LBM3 on both sides of M.

As described above, each photodetector element SE1 of the photodetector SE
Five spectroscopic LB1s detected by 1, SEM1, SE31, SEM2, SEM3
1, LBM1, LB31, LBM2, LBM3 are used as shown in FIG. That is, a focus error signal is generated based on the output signal of the photodetector element SEM1. In addition, a pit reproduction signal (= signal corresponding to the intensity of the pit reflected light) is generated based on the sum of the output signals of the photodetector elements SEM2 and SEM3, and based on the difference between the output signals of the photodetector elements SEM2 and SEM3. ,
A magneto-optical reproduction signal (= signal corresponding to the rotation angle of the polarization plane of the pit reflected light) is generated. Here, the system controller controls switching between reproduction of information based on a pit reproduction signal or reproduction of information based on a magneto-optical reproduction signal. That is, when reproducing the pit portion, the record information is reproduced based on the pit reproduction signal, and when reproducing the land portion, the record information is reproduced based on the magneto-optical reproduction signal.

A tracking error signal is generated from the difference between the output signals of the photodetectors SE11 and SE31. The polarity of the tracking error signal needs to be inverted when the pit portion is reproduced and when the land portion is recorded / reproduced. That is, as shown in FIG. 4, since the area of the negative feedback loop is different between the pit portion and the land portion, “SE11-SE
31 ”is used as the tracking error signal, or conversely“ SE31-
It is necessary to switch whether "SE11" is used as a tracking error signal, and this switching is controlled by the system controller.

In the system controller, as described above,
In addition to the switching control of the pit reproduction signal / magneto-optical reproduction signal and the switching control of the polarity of the tracking error signal,
As shown in FIG. 4, the output of laser light is switched between low power and high power in response to the switching of the designation of the reproduction mode / recording mode, or the input data at the time of recording. Is sent from the encoder to the modulation circuit to drive the magnetic head 60, thereby performing control for realizing magnetic recording by the magnetic field modulation method. In addition, specify the playback mode / recording mode,
The pit reproduction mode / magneto-optical reproduction mode can be designated by an input from the operation display unit or by a command from another computer device or the like.

In the above embodiment, the magneto-optical recording / reproducing is performed on the land portion by the magnetic field modulation method, but it is also possible to record / reproduce information on the land portion by another method.
For example, in the case of recording / reproducing in the phase change type, the MO signal of FIG. 2B becomes unnecessary, and the information may be reproduced based on only the pit signal. Further, if the magneto-optical recording / reproducing is performed by the light intensity modulation method instead of the magnetic field modulation method, the standard among the recording powers having two high powers to be switched by the power switching means of claim 1. The power may be changed so that the information processing means sends the input information not to the drive circuit of the magnetic head but to the drive circuit of the laser.

[0016]

As described above, according to the present invention, new information can be recorded on the land portion in addition to the information recorded as pits, so that the optical disc can be used without changing the laser wavelength or the numerical aperture NA of the objective lens. The recording density of can be substantially increased. Moreover, it is easy to rewrite the information newly recorded in the land portion.

[Brief description of drawings]

FIG. 1A is an explanatory diagram showing a relationship between three spots and pits on a disc surface, and FIG. 1B is a schematic diagram showing an optical system of an example apparatus.

2A is a schematic diagram of a photodetector used in the apparatus of the embodiment, and FIG. 2B is an explanatory diagram showing processing of an output signal of the photodetector.

FIG. 3 is a block diagram showing a circuit configuration of a main part of the embodiment apparatus.

FIG. 4 is an explanatory diagram showing a tracking polarity of the apparatus of the embodiment.

Claims (3)

[Claims] 1. An optical disc in which information is recorded as pits on a disc surface and a rewritable recording film of information is formed on at least a land portion. 2. In a mode for reproducing information, a laser beam of low power is applied to a disk to reproduce information based on reflected light, and in a mode of writing information, a high power laser beam is written. An optical disc recording / reproducing apparatus for irradiating a disc with the light to set the state of a recording film to a state corresponding to information, and a pit reproducing mode for reproducing information recorded as pits and a state of a recording film. A recording film reproducing mode for reproducing the information recorded as a recording film, and a recording film writing mode for writing the information as a recording film state, and a pit reproducing mode. An optical disk recording / reproducing apparatus having polarity switching means for switching the polarity of tracking control so that the pit portion is tracked in the recording film reproducing mode and the land portion is tracked in the recording film reproducing mode or the recording film writing mode. 3. An optical disk recording / reproducing in which a low power laser beam is applied to a disc in a mode for reproducing information and a high power laser beam is irradiated in a mode for writing information. The apparatus is a pit reproduction mode for reproducing information recorded as pits, a recording film reproduction mode for reproducing information recorded as magnetization directions, and a recording for writing information as magnetization directions. A mode designating means for designating any one of the film writing modes, a tracking control means for controlling tracking by a three-spot method, and a pit portion in the pit reproducing mode are tracked to reproduce a recording film. Alternatively, in the recording film writing mode, a polarity switching means for switching the polarity of tracking control so that the land portion is tracked, and in the pit reproducing mode, the intensity of the reflected light of the main spot is compared. The signal to be processed as a reproduction signal, a recording film reproducing mode -
In the recording mode, a signal corresponding to the rotation angle of the plane of polarization of the reflected light of the main spot is processed as a reproduction signal, and in the recording film writing mode, the input information is processed to generate a magnetic field modulation signal. An optical disc recording / reproducing apparatus comprising: an input information processing means for applying the magnetic field modulation signal to a drive circuit of a magnetic head.