JPH07262582A - Optical information recording and reproducing device and optical information recording and reproducing system - Google Patents

Abstract

PURPOSE:To reduce cross talk due to a tilt using simplified constitution of the device by selecting a beam for signal reproduction in every prescribed area from plural beams transmitted from a semiconductor laser in accordance with the tilt of an optical disk at the time of information reproduction. CONSTITUTION:Three beams transmitted from a semiconductor laser 1 are converged on an optical disk 5 as three spots with every interval of 157mum in the radial direction of the optical disk 5 by means of an optical system. The reflected light beam of the disk 5 is converged on the prescribed positions of the respective light receiving areas of an RF signal detecting sensor 10 and a servo sensor 9 by means of the optical system. The sensors 10, 9 perform the detection of an RF signal, focusing servo and tracking servo independent of the respective three beams. At the time of signal reproduction, a control part changes the beam to the beams for reproduction and servo selected in accordance with the tilt by using the amount of cross talk measured in every area of the optical disk 5 and reproduces the signal. Consequently, the cross talk from an adjacent track due to the tilt is reduced by using the simple constitution of the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus and an optical information recording / reproducing system for converging a light beam emitted from a light source on an optical disk to record / reproduce information.

[0002]

2. Description of the Related Art In the field of memories related to optical disks,
Increasing recording density is one of the major technical issues,
For example, in the case of optical discs such as 5.25 inches and 3.5 inches, the first generation ISO (International Organiza
direction for standardization)
Many proposals have been made for use in the next generation with a high recording density in the radial direction. In these, the recording density in the linear direction is increased by a modulation method or an encoding technique, and the density in the radial direction is increased by narrowing the track interval as much as possible.

On the other hand, in order to increase the recording density, the wavelength of the recording light beam is shortened and the size of the beam spot for recording is reduced. Hereinafter, the latter case of increasing the recording density by reducing the beam spot diameter for recording will be described.

When the recording density is increased by reducing the size of the beam spot, the beam spot diameter can be reduced by increasing the NA (numerical aperture) of the pickup lens. However, if the beam spot diameter is reduced in this way, the recording density can be increased, but this will deteriorate the yield during lens manufacturing, and the degree of influence due to disc manufacturing error (for example, disc plate There is a problem that the thickness and the degree of influence on the warp increase. In particular, the degree of influence on the tilt (warp) of the optical disk caused by the environmental temperature and the time factor becomes strong.

When the optical disc is tilted, the tilt causes coma aberration in the reading optical system during signal reproduction. This coma aberration is proportional to the cube of NA and is an asymmetrical aberration that has a tail in the direction in which tilt occurs. Therefore, when a recorded signal is reproduced, signal leakage from adjacent tracks (crossing) occurs. Talk) will occur.

To solve the above-mentioned problem of crosstalk, conventionally, the recording signal is reproduced by the following two methods. One method is to read the signals of the track on which the original signals are recorded and the tracks adjacent to the tracks at the same time by using three light beams, and based on the phase of each of the read signals during signal processing. Another method is to provide a photodetection optical system for detecting tilt separately from the optical head for reading the optical disc, and to perform the entire optical head based on the result detected by the photodetection optical system. It is a method to read the signal while tilting. These methods have reduced the above-mentioned crosstalk.

[0007]

However, in reproducing the recording signal with the above-mentioned conventional crosstalk reduced,
There are the following problems.

In the former method of simultaneously reading the signals of three tracks using the three beams, it is difficult to set the phase relationship between the signal used for correction and the original signal and the coefficient used for correction. There is the problem of complexity.

In the latter method of tilting the optical head,
There is a drawback that an extra mechanism is required, which leads to an increase in size and cost of the device, and further, since the direct effect is not detected by the beam used for recording and reproducing, there is a possibility that the device will change over time. There is a problem that the tilt of the optical head with respect to the tilt is deviated, and crosstalk occurs during reading.

An object of the present invention is to provide an optical information recording / reproducing apparatus capable of easily reducing crosstalk caused by tilting of a disc having a recording capacity improved by narrowing a track.

[0011]

An optical information recording / reproducing apparatus of the present invention has a plurality of light emitting sources, and collects information by converging each light beam emitted from each light emitting source on a disk-shaped recording medium. An optical information recording / reproducing apparatus for recording / reproducing, wherein each light beam emitted from the plurality of light emitting sources is directed toward the recording medium so that each light beam converges at a predetermined interval in a radial direction of the disc. An optical system that emits at different emission angles, and an RF signal detection unit that detects an RF signal using any one of the light beams emitted from the optical system,
The control means has an adjusting means for focusing and tracking any one of the light fluxes emitted from the optical system, and a control means for controlling switching of the light fluxes in the RF signal detecting means and the adjusting means. At the time of information reproduction, the RF signal detecting means is caused to detect an RF signal in a predetermined region of the recording medium for each light beam, and the light beam for information reproduction in the predetermined region is detected based on the detection result. Select from each luminous flux,
It is characterized in that the adjusting means is caused to perform focusing and tracking using the selected light flux for reproducing information, and the RF signal detecting means is made to detect an RF signal.

In the above-mentioned optical information recording / reproducing apparatus, the control means divides the recording medium into a plurality of areas consisting of a plurality of tracks in the radial direction of the disc, and when reproducing information, the RF signal detecting means includes the plurality of areas. The RF signal is detected in each region for each of the light fluxes, and the information reproducing light fluxes in the plurality of regions are selected from the light fluxes based on the detection result, and the information in which the plurality of regions are selected is selected. The light flux is switched in the adjusting means and the RF signal detecting means so that the light flux for reproduction is reproduced.

Further, the optical information recording / reproducing system of the present invention comprises an optical information recording / reproducing apparatus for recording / reproducing information by converging a light beam emitted from a light source onto a disc-shaped recording medium by a pickup lens. In the optical information recording / reproducing system with the recording medium having the track, the recording medium is provided on a predetermined track so as to be opposite to each other in the disc radial direction with the center of the predetermined track as a boundary. First and second tilt detection pits formed by giving a certain amount of offset in the outer and inner directions are provided, and the optical information recording / reproducing apparatus has a lens for adjusting the tilt angle of the optical axis of the pickup lens. Tilting means, RF signal detecting means for detecting an RF signal using the light flux emitted from the pickup lens; An adjusting means for focusing and tracking a light beam emitted from the up lens, and a control means for controlling the lens tilt means so that the tilt angle of the pickup lens used in the RF signal detecting means and the adjusting means becomes a predetermined angle. The control means is provided, and at the time of information reproduction, the first and second control signals detected by the RF signal detection means.
The lens tilt means is controlled so that the difference in signal amplitude in the tilt detection pit is minimized.

[0014]

In the optical information recording / reproducing apparatus of the present invention configured as described above, a plurality of light beams having different incident angles with respect to the recording medium are used as information reproducing light beams. At the time of information reproduction, the information reproduction light beam is switched to the information reproduction light beam with less crosstalk according to the tilt of the recording medium for each predetermined area, so that the crosstalk caused by the tilt of the recording medium is easily corrected. be able to. Therefore, in the present invention, it is not necessary to perform complicated signal processing such as setting the phase relationship between the correction signal and the original signal and the coefficient used for correction as in the prior art.

Further, in the optical information recording / reproducing system of the present invention, the recording medium in which the tilt detecting pit is formed in each predetermined area is used, and the tilt of the pickup lens is determined based on the signal obtained from the tilt detecting pit. Adjusted. At the time of information reproduction, the optical axis tilt angle of the information reproduction pickup lens with respect to the recording medium is adjusted in accordance with the tilt of the recording medium in each of the above-mentioned predetermined regions, so that crosstalk caused by the tilt of the recording medium can be simplified. Therefore, there is no possibility that the tilt of the optical head with respect to the tilt of the recording medium is deviated due to the change with time of the apparatus and crosstalk occurs during reading as in the conventional case.

[0016]

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

FIG. 1 is a schematic configuration diagram of a main optical system of an optical information recording / reproducing apparatus according to a first embodiment of the present invention.

The optical information recording / reproducing apparatus of this embodiment has three
Among the beams emitted from the semiconductor laser 1 in which one light emitting source is arranged in an array, one of them is selected according to the tilt of the optical disc 5 to reproduce a signal.
The structure is such that a semiconductor laser 1, a collimator lens 2, a polarization beam splitter 3, and a quarter-wave plate 1 which are sequentially arranged in a traveling direction of a light beam emitted from the semiconductor laser 1.
3, a pickup objective lens 4, a beam splitter 6, a condenser lens 7 and an RF, which are sequentially arranged in the traveling direction of the light reflected by the polarization beam splitter 3.
It is composed of a signal detecting sensor 10, a condenser lens 8 and a servo sensor 9 which are sequentially arranged in the traveling direction of the light reflected by the beam splitter 6.

In the above optical information recording / reproducing apparatus, the semiconductor laser 1 is provided so that the arrangement directions of the light emitted from the three light emitting sources on the optical disc 5 coincide with the radial direction of the optical disc 5. . In addition, the semiconductor laser 1
The three light-emitting sources are provided so that their intervals are 100 μm, and when the beams emitted from the three light-sources are focused on the recording surface of the optical disk 5, the interval is 1
It has been reduced to 5 μm.

The pickup objective lens 4 has a focal length 5
mm is used, and in this case, the optical disc 5
The angle of view of each beam on the recording surface of is 0.015 /
It is 5≈3 milliradians. Further, among the three beams emitted from the pickup objective lens 4, when the optical disc 5 has no tilt, the central beam is substantially perpendicular to the recording surface of the optical disc 5, and the left and right beams are respectively in opposite directions. It is preset so that the light is incident at an angle of milliradian.

Each of the servo sensor 9 and the RF signal detecting sensor 10 is emitted from the semiconductor laser 1 3
It has three light receiving regions respectively corresponding to one beam, and each light receiving region can independently perform servo or RF signal detection. Therefore,
In the apparatus of this embodiment, a focusing servo for focusing a beam on the recording surface of the optical disc 5 with a predetermined spot diameter,
The tracking servo that causes the focused spot to always follow the track and the RF signal detection can be performed by each of the three beams emitted from the light emission source.

Further, the servo sensor 9 and the RF signal detecting sensor 10 are respectively connected to control means (not shown), and the control means controls switching of the luminous flux in the servo sensor 9 and the RF signal detecting sensor 10. .

Next, the operation of the above optical information recording / reproducing apparatus will be described.

The three light beams emitted from the semiconductor laser 1 are collimated by the collimator lens 2, transmitted through the polarization beam splitter 3 and the quarter-wave plate 13, and picked up by the objective lens 4 onto the recording surface of the optical disk 5. Each is focused.

The reflected light from the optical disk 5 enters the polarization beam splitter 3 via the pickup objective lens 4 and the quarter wavelength plate 13. At this time, the polarization direction of the light is converted by the action of the quarter-wave plate 13 into a direction orthogonal to the direction of incidence, and all the light is reflected by the polarization beam splitter 3. The light reflected by the polarization beam splitter 3 is split into two different optical paths, one light is transmitted through the beam splitter 6 and enters the condenser lens 7, and the other light is reflected by the beam splitter 6. And enters the condenser lens 8. The light incident on the condenser lens 7 is condensed on the light receiving area of the RF signal detecting sensor 10, and the light incident on the condenser lens 8 is condensed on the light receiving area of the servo sensor 9. At this time, in the light receiving regions of the servo sensor 9 and the RF signal detecting sensor 10, the three lights emitted from the semiconductor laser 1 are collected at predetermined positions.

In the above optical information recording / reproducing apparatus,
When information is recorded on the optical disc 5, the central beam among the three beams emitted from the semiconductor laser 1 is used for the recording. When recording, first
Focusing servo and tracking servo are applied to the track to be recorded using the central beam, and then the central beam is intensity-modulated according to information to form a pit on the recording surface of the optical disk 5. As a result, information is recorded on the optical disc 5.

When the information recorded as described above is reproduced, crosstalk from adjacent tracks due to the tilt of the optical disc 5 becomes a problem. Hereinafter, a method of correcting this crosstalk will be described.

In the optical information recording / reproducing apparatus of this embodiment,
When reproducing the signal recorded on the optical disk 5, the signal reproducing beam is selected from the three beams emitted from the semiconductor laser 1 for each predetermined area by a control unit (not shown), and the selected beam is used. The recorded signal is reproduced. The selection of the reproduction beam by the control means will be described below.

FIG. 2 shows the laser beam emitted from the semiconductor laser 1.
In the schematic diagram showing the state where the three beams are focused on the optical disc 5, A, B and C represent the respective spots on which the three beams are focused on the optical disc 5, and the spots A, B and C are the respective spots. The optical discs 5 are focused in the radial direction at intervals of 15 μm.

As shown in FIG. 2, the track of the optical disk 5 has a structure in which land portions where information is recorded and groove portions where information is not recorded are alternately provided. The spot A is on the land portion 11-1 located on the outer side in the radial direction of the optical disk 5, the spot C is on the land portion 11-5 located on the inner side, and the spot B is between the spots A and C. Is located on the land portion 11-3 located at.

Now, consider the central spot B. A groove portion 12-4 and a groove portion 12-3 are provided inside and outside the land portion 11-3 where the central spot B is located, and further inside and outside the land portion 11-4 and the land portion 11-2. There is. It is assumed that each land portion has been erased in advance.

First, a signal having a constant frequency is recorded on the land portion 11-3 by using the spot B at the center. Next, the spot B is moved to the land portion 11-2 and reproduced, and the amount of crosstalk from the land portion 11-3 in the land portion 11-2 is measured. This time spot B is land part 11
-4, and similarly, the amount of crosstalk from the land portion 11-3 in the land portion 11-4 is measured. In this way, the amount of crosstalk concerning the spot B near the land 11-3, that is, the central beam of the beams emitted from the semiconductor laser 1 is measured.

Next, the pickup objective lens 4 is sought to change the spot C from the land portion 11 where the spot B was located.
Move to position 3. Then, the moved spot C
Regarding the above-mentioned land portion 11-2 and land portion 11
-4, the amount of crosstalk from the land portion 11-3 is measured.

Further, similarly to the case of the spot C, the pickup objective lens 4 is sought to move the spot A to the position of the land portion 11-3, and the land portion 11 is moved.
-2 and the land portion 11-4, the amount of crosstalk from the land portion 11-3 is measured.

As described above, each spot A, B,
C, that is, the amount of crosstalk in the vicinity of the land portion 11-3 for each beam emitted from the semiconductor laser 1 is measured.

When the crosstalk amount of each beam is measured, the land portion 1 in each spot A, B, C is then measured.
The difference between the crosstalk amounts of 1-2 and the land portion 11-4 is obtained, and the obtained difference between the crosstalk amounts is the smallest, and the crosstalk amount is the predetermined value or less. It is selected as a reproducing beam in the vicinity of 3.

The selection of the reproduction beam as described above is carried out over the entire optical disk 5 for each predetermined area, and at the time of signal reproduction, the control means switches the reproduction beam to the selected reproduction beam for each area and Playback is performed.
For example, the entire surface of the optical disk 5 is divided into a plurality of zones for each of a plurality of tracks in the radial direction of the disk, a reproduction beam is selected for each of the divided zones, and a reproduction beam is switched for each zone to reproduce a signal. To do. As a result, good signal reproduction can be performed over the entire optical disc 5 with little crosstalk.

In the optical information recording / reproducing apparatus of this embodiment, the incident angle of each beam focused by the pickup objective lens 4 on the optical disk 5 is 0 for the central beam and ± 3 milliradian for the other two beams. However, since the tilt amount of the optical disc is regulated to 5 milliradians or less in the first-generation ISO standard, the tilt that normally occurs in the optical disc is sufficiently tolerable.
Therefore, the crosstalk caused by the tilt can be corrected to a sufficiently practical range.

Further, in the optical information recording / reproducing apparatus of the present embodiment, the semiconductor laser 1 has three light emitting sources, and three beams are emitted by this.
The beam emitted from one light emitting source may be divided into three.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a schematic block diagram of the main optical system of the optical information recording / reproducing apparatus of the second embodiment of the present invention.

In the optical information recording / reproducing apparatus of this embodiment, the pickup objective lens 4 is provided with the lens tilt mechanism 22, and instead of the semiconductor laser 1, the semiconductor laser 21 having only one light emitting source is used. Corresponding to that, the servo sensor 9 and the RF signal detecting sensor 10 are replaced by the servo sensor 19 and the RF signal detecting sensor 20 each having one light receiving area, respectively.
This is the same device as the optical information recording / reproducing device of the embodiment. The same components as those of the optical information recording / reproducing apparatus of the first embodiment are designated by the same reference numerals.

In the above optical information recording / reproducing apparatus, the lens tilt mechanism 22 is a cantilever or the like attached to the objective lens, and is integrated with the actuator mechanism (not shown) of the pickup objective lens 4. The lens tilt mechanism 22 is controlled by a control unit (not shown), and the angle of the pickup objective lens 4 is controlled according to the tilt of the optical disc 15.

Next, the operation of the above-mentioned optical information recording / reproducing apparatus will be described.

FIG. 4 is a schematic diagram showing the tracks of the optical disc 15 used in the optical information recording / reproducing apparatus shown in FIG. 3, and the tracks provided on the surface of the recording medium for detecting the tilt of the disc. It is a principal part enlarged view of 30.

In FIG. 4, the track 30 is composed of a land portion 31 and groove portions 32, 32 'like other tracks. The land portion 31 includes the land portion 31.
Tilt detection pits 33 and 34 formed by offsetting a predetermined amount, for example, 0.5 μm in the outer and inner directions so as to be opposite to the radial direction of the disc, are provided with the center of the boundary as a boundary. There is. Such pits are similar to the so-called wobble pits of the so-called sample servo format.
It is formed at several predetermined positions on the outer circumference.

In this embodiment, an optical information recording / reproducing apparatus shown in FIG. 3 and an optical information recording / reproducing system shown in FIG. 4 form an optical information recording / reproducing system. When the disc is inserted, the signals of the tilt detection pits 33 and 34 are first measured by the following procedure.

First, the signals of the tilt detection pits provided on the innermost circumference of the disc are sequentially reproduced. If the amplitude of the reproduced signal is unbalanced (the difference between the absolute values of the amplitudes of the waveforms obtained from the reproduced signal is large), the pickup objective lens 4 is tilted by using the lens tilt mechanism 22 and the tilt detecting pit is again detected. The signals of are sequentially reproduced.
By repeating such an operation several times, the coma aberration generated by tilting the lens and the coma aberration generated by the tilt of the disk cancel each other to determine the tilt of the lens with which the unbalance is minimized. As a result, the tilt of the pickup objective lens 4 on the inner circumference of the optical disc 15 is determined.

Next, the above-mentioned operations are repeated for the middle and outer circumferences of the optical disk 15 to determine the optimum lens inclinations at the middle and outer circumferences. The tilt of the pickup objective lens 4 at each of the inner, middle, and outer positions thus determined is stored based on the radius of the optical disc 15.

Pickup objective lens 4 at each position
When the tilt of the pickup objective lens 4 is stored, the tilt of the pickup objective lens 4 is automatically switched depending on the radius while the optical disk 15 is used thereafter. That is, when reproducing a signal, the pickup objective lens 4 is automatically switched from its position (position based on the disk radius) to an inclination according to the tilt of the optical disk 15, and the reproduction of the signal on the optical disk 15 is always the best. Playback is performed in a state in which the influence of crosstalk is small and the signal quality is good.

In the optical information recording / reproducing apparatus of this embodiment, the tilt of the pickup objective lens 4 is determined by using the tilt detecting pit, but the zone CAV (Constant A
In the case of a disc formatted with ngu-lar velocity, the tilt of the pickup objective lens 4 is determined by using the pre-pit (header signal) formed at each zone boundary instead of the tilt detection pit. May be.

[0052]

Since the present invention is constructed as described above, it has the following effects.

According to the first and second aspects of the present invention, there is no need for complicated signal processing as in the conventional case, and crosstalk from adjacent tracks due to tilt of the optical disk can be easily suppressed with a simple structure. Therefore, there is an effect that the size and cost of the device can be reduced.

Further, since the light flux actually used for recording / reproducing is corrected according to the tilt of the optical disk, there is no fear that the tilt of the optical head will deviate from the tilt of the recording medium, and the reliability of the apparatus is improved. There is an effect of doing.

According to the third aspect of the present invention, since an extra mechanism such as a tilt detecting mechanism unlike the conventional one is not required, there is an effect that the size and cost of the device can be reduced. Further, since the light flux actually used for recording / reproduction is corrected according to the tilt of the optical disc, there is no possibility that the tilt of the optical head with respect to the tilt of the recording medium will deviate due to the change with time of the device as in the conventional case. This has the effect of improving the reliability of the device.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main optical system of an optical information recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 shows 3 emitted from a semiconductor laser 1 in FIG.
FIG. 3 is a schematic diagram showing a state in which two beams are focused on an optical disc 5.

FIG. 3 is a schematic configuration diagram of a main optical system of an optical information recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram showing tracks of an optical disc 15 used in the optical information recording / reproducing apparatus shown in FIG.

[Explanation of symbols]

 1, 21 Semiconductor laser 2 Collimator lens 3 Polarization beam splitter 4 Pickup objective lens 5 Optical disc 6 Beam splitter 7, 8 Condensing lens 9, 19 Servo sensor 10, 20 RF signal detection sensor 13 1/4 wavelength plate 22 Lens tilt Mechanism 30 tracks A, B, C spots

Claims (3)

[Claims] 1. An optical information recording / reproducing apparatus having a plurality of light emitting sources, wherein each light beam emitted from each light emitting source is focused on a disk-shaped recording medium to record / reproduce information. And an optical system that emits the respective light beams emitted from the light emission source toward the recording medium at different emission angles so that the respective light beams converge at a predetermined interval in the radial direction of the disc. RF signal detecting means for detecting an RF signal using any one of the luminous fluxes, adjusting means for focusing and tracking any one of the luminous fluxes emitted from the optical system, and the RF signal. A signal detecting means and a controlling means for controlling switching of light fluxes in the adjusting means, wherein the controlling means places the recording medium in the RF signal detecting means during information reproduction. The detection of the RF signal in the region is performed for each light flux, and the information reproduction light flux in the predetermined region is selected from the respective light fluxes based on the detection result, and the selected information reproduction light flux is used. An optical information recording / reproducing apparatus characterized in that the adjusting means is caused to perform focusing and tracking, and the RF signal detecting means is made to detect an RF signal. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the control means divides the recording medium into a plurality of areas composed of a plurality of tracks in a disc radial direction, and when reproducing information,
The RF signal detecting means is caused to detect the RF signals in the plurality of regions for each light flux, and the information reproducing light flux in the plurality of regions is selected from the respective light fluxes based on the detection result. An optical information recording / reproducing apparatus, characterized in that the light flux is switched in the adjusting means and the RF signal detecting means so that a plurality of areas are reproduced by a selected light flux for information reproduction. 3. An optical information recording / reproducing apparatus for condensing a light beam emitted from a light source onto a disc-shaped recording medium by a pickup lens to record / reproduce information, and an optical information by a recording medium having a plurality of tracks. In the recording / reproducing system, a predetermined track is provided on the recording medium with a predetermined amount of offset in the outer and inner directions so as to be opposite to each other with respect to the center of the predetermined track with respect to the disc radial direction. First and second tilt detection pits are formed, and in the optical information recording / reproducing apparatus, lens tilt means for adjusting the tilt angle of the optical axis of the pickup lens, and light emitted from the pickup lens. R using luminous flux
An RF signal detecting means for detecting an F signal, an adjusting means for focusing and tracking a light beam emitted from the pickup lens, and a tilt angle of a pickup lens used for the RF signal detecting means and the adjusting means are set to a predetermined angle. And a control means for controlling the lens tilt means so that the first and second tilt detections detected by the RF signal detection means at the time of information reproduction. An optical information recording / reproducing system, characterized in that the lens tilting means is controlled in a state in which the difference in amplitude of signals in the use pit is minimized.