JPH11250486A - Information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the level of a leak-in signal more surely by making the transmission state of light beams in the sectional plane of an optical path settable while changing the transmissivity and/or the shape of a mask area to make a device cope with objective areas of reproduction flexibly. SOLUTION: Reading of information recorded in respective zones of an optical disk is performed by changing the mask pattern of an EC plate 17h and, moreover, ratios of levels of leak-in signals with respect to the levels of recording signals (signal ratios) are calculated as to mask patterns suppressing the levels of leak in signals. A master control circuit 21 recognizes optimum maser patterns of respective zones by storing ON/OFF information of maser patterns with which these signal ratios become the smallest in a correspondence table by associating them with respective zone numbers. Thus, the level of the leak-in signal is surely suppressed by the maser patterns to be set to the EC plate 17h based on this correspondence table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an information reproducing apparatus for reproducing information from an optical disk.

[0002]

2. Description of the Related Art In recent years, it has been required to increase the capacity of optical discs. In order to respond to the demand for large capacity, both a technique for recording information at a high density and a technique for accurately reproducing information recorded at a high density are required. In the recording of information, recording marks have been reduced by brush tip recording, magnetic field modulation recording, and the like, and attempts to reduce the track pitch have already been made.

On the other hand, in information reproduction, it is desired to reduce the spot of a reproduction beam irradiated on an optical disk to a size capable of detecting a single recording mark. Have difficulty. FIG.
FIG. 3 is a diagram for explaining information reproduction by a current optical disk drive device. FIG. 6 shows an optical disc 100 and a beam spot 101 of a reproduction beam applied to the optical disc 100. The reproduction beam is narrowed by the optical system to near its diffraction limit, but penetrates not only to the recording track 103 to be reproduced but also to an adjacent recording track (adjacent track) 105.

Therefore, a signal (leakage signal) generated according to information written in the adjacent track 105 is mixed in a reproduction signal generated in accordance with the reflected light (reflected beam) of the reproduction beam. Become. However, the level of the leak signal is a signal (recording signal) that should be acquired originally.
Since it is sufficiently smaller than, it does not affect information reproduction. Therefore, in the current optical disk drive device, the spot 101 of the reproduction beam is positioned on the adjacent track 105 in this manner.
It is allowed to invade.

However, if it is attempted to further reduce the track pitch of the current optical disk, the level of the leak signal increases with the reduction. Therefore, it is difficult to detect a recording signal to be originally obtained from a reproduction signal. Therefore, it has been proposed to provide a spatial filter in the optical path of the reflected beam in the optical disk drive. This spatial filter has a function of blocking (or dimming) a region of the cross section of the reflected beam through which a light wave (leakage light) contributing to a leak signal passes. In this way, the level of the leak signal is reduced to an acceptable value.

[0006]

However, even if a spatial filter is provided in the optical disk drive, if different types of optical disks or the same type of optical disk are loaded with different recording formats, the optical path of the reflected beam will be reduced. The amplitude distribution of the leaked light and the amplitude level of the entire leaked light also change. That is, the area to be shielded (or dimmed) in the cross section of the reproduction beam often differs depending on the optical disk.

Therefore, when an optical disc is treated as a replaceable medium, a leak signal is not always suppressed, and a situation may occur in which a spatial filter conversely lowers the level of a recording signal to be originally acquired. Even on the same optical disk, the amplitude distribution of leaked light may differ depending on the radial position of the area to be reproduced. This is because the servo characteristics of tracking and focusing and the polarization characteristics of the substrate constituting the optical disk change depending on the curvature of the recording track. Therefore, even when information is reproduced from the same disk, the spatial filter cannot always suppress the leak signal.

The present invention has been made in view of such a problem, and is an information capable of more reliably suppressing the level of a leak signal by flexibly responding to the type of an optical disc and a reproduction target area on the optical disc. It is an object to provide a playback device.

[0009]

According to a first aspect of the present invention, there is provided a reproducing system for reproducing information based on reflected light of a reproducing beam applied to a recording medium, a mask disposed on an optical path of the reflected light, and a mask. A spatial filter capable of changing the transmittance and / or shape of the region, and the transmittance and / or
Alternatively, a controller is provided for setting the light transmission state in the cross section of the optical path by changing the shape.

According to a second aspect of the present invention, a reproducing system for reproducing information based on reflected light of a reproducing beam applied to a recording medium can be inserted into an optical path of a reflected light separately from a reproducing system. A plurality of spatial filters having different transmittances and / or shapes in the mask region, and a controller that sets one of the plurality of spatial filters in the optical path of the reflected light to set a light transmission state in a cross section of the optical path. And characterized in that:

According to a third aspect of the present invention, in the information reproducing apparatus according to the first or second aspect, the controller performs the setting according to the type and / or recording format of the recording medium. . According to a fourth aspect of the present invention, in the information reproducing apparatus according to any one of the first to third aspects, the recording medium is an optical disk;
The controller performs the setting in accordance with the radial position on the optical disk to which the reproduction beam is irradiated.

According to a fifth aspect of the present invention, in the information reproducing apparatus according to the fourth aspect, the optical disk is a recording medium to which a land / groove recording method is applied, and the controller is configured to irradiate a reproduction beam on the optical disk. It is characterized in that the setting is performed in accordance with whether the position is a land portion or a groove portion. According to a sixth aspect of the present invention, in the information reproducing apparatus according to any one of the first to fifth aspects, the content of the setting by the controller is predetermined according to an aberration of an optical system provided in the reproducing system. It is characterized by being able to.

According to a seventh aspect of the present invention, in the information reproducing apparatus according to any one of the first to sixth aspects, the controller evaluates a quality of a reproduction signal obtained by a reproduction system,
The setting is performed based on the result.

[0014]

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

First, a first embodiment according to the present invention will be described with reference to FIGS. 1, 2 and 3. First Embodiment (Configuration of Optical Disk Drive) FIG. 1 is a diagram showing a main configuration of an optical disk drive 1.

The optical disk drive 1 includes the following components. That is, a control unit 11 for executing a recording or reproduction command from a host computer, a reproduction circuit 13 for generating a data bit string according to a reproduction signal obtained from an optical disk under the instruction of the control unit 11, and irradiation to the optical disk A recording circuit 15 for defining a light waveform,
An optical pickup 17 that accesses each area of the optical disk and irradiates a light (reproduction beam or recording beam) having a prescribed waveform and receives a reflected beam, the movement of the optical pickup 17 and the objective lens 1 in the optical pickup 17
Servo mechanism 19 for moving 7d, optical pickup 17
A mask control circuit 21 for setting a mask pattern of an EC plate 17h (to be described later), a rotation mechanism (not shown) for rotating the optical disk, and a magnetic field source (not shown) for applying a magnetic field to the optical disk.

The optical pickup 1 shown in FIG.
7 includes, as an emission system, a semiconductor laser 17a, a collimator lens 17b for collimating the emitted light of the semiconductor laser 17a, a mirror 17c for focusing a laser spot on an optical disk, and an objective lens 17d. When recording or reproducing information, the recording circuit 15 drives the semiconductor laser 17a to cause the optical pickup 17 to appropriately emit a reproduction beam having a constant intensity and a recording beam intensity-modulated according to data to be recorded.

The optical pickup 17 has, as a light receiving system, a beam splitter 17 for splitting a reflected beam incident from an optical disk via a mirror 17c into two light beams.
e, a condensing lens 17 for condensing one of the two light rays
f, a light detecting element 17g for receiving the collected light is provided. The reflected beam is converted into an electric signal (reproduced signal) corresponding to the intensity by the light detecting element 17g, and thereafter, the reproducing circuit 13 performs each process of reproduction.

In the light receiving system, an EC plate 17h as a spatial filter is inserted between the beam splitter 17e and the condenser lens 17f. EC board 17h
Forms a mask pattern that can be changed by the mask control circuit 21 on the cross section of the reflected beam.

The optical pickup 17 includes, as another light receiving system, a beam splitter 17i for obtaining the other light beam split by the beam splitter 17e, a light beam incident from the beam splitter 17i, and a cross section of the light beam. Lens unit 17j to be deformed, detector 17 for receiving light rays emitted from lens unit 17j
k. In the detector 17k, a focus error signal and a tracking error signal, which are electric signals according to the intensity distribution of the image formed on the light receiving surface, are generated and sent to the servo mechanism 19, respectively. The servo mechanism 19 finely moves the optical pickup 17 itself or the objective lens 17d of the optical pickup 17 in the radial direction of the optical disk based on the tracking error signal. This implements a tracking servo that causes the light emitted from the optical pickup 17 to follow the recording track of the optical disk. Further, the servo mechanism 19 finely moves the objective lens 17d of the optical pickup 17 in a direction perpendicular to the optical disk surface based on the focus error signal. This realizes a focus servo that focuses the beam waist on the information recording surface of the optical disc.

FIG. 2 is a diagram for explaining the configuration of the EC plate 17h. The EC board 17h has an existing EC (Ele
In the area S1 corresponding to the vertical section of the reflected beam, four segments 17h1 to 17h4 are arranged side by side in the Y direction corresponding to the width direction of the recording track. Each segment 17h1-
The electrodes 17h4 are all connected to the mask control circuit 2 in FIG.
1 and the mask control circuit 21 has a driver for individually driving the segments 17h1 to 17h4.

Not driven by the driver (OFF
The segment (in the state) is a transparent area which is a transparent area in the EC plate 17h, and the segment (in the ON state) driven by the driver is a semi-transparent or light-shielded mask area in the EC plate 17h. Become.

The mask control circuit 21 controls each segment 17
There is a correspondence table relating to ON / OFF combinations of h1 to 17h4, and each segment 17h according to this correspondence table.
By individually turning on / off 1-17h4,
Various mask patterns exemplified in FIGS. 3A, 3B, and 3C can be set. In FIG. 3, a hatched portion is a mask region, and a non-hatched portion is a transmission region.

(Operation of Optical Disk Drive) In the optical disk drive 1 described above, the control unit 11 which has received a command from the host computer responds to the command by a rotating mechanism (not shown), a magnetic field generating source (not shown), Servo mechanism 19, recording circuit 15, reproducing circuit 13, mask control circuit 2
1 are driven.

The control unit 11 performs the following operation particularly during reproduction. That is, when a reproduction command is received from the host computer, it is determined which of a plurality of zones formed by radially dividing the optical disk the recording track on the optical disk to be reproduced is included. Then, the number of the zone to which the recording track belongs is given to the mask control circuit 21.

The correspondence table of the mask control circuit 21 contains all the zone numbers and the respective segments of the EC board 17h in advance (FIG. 2).
ON / OFF information is registered. When the zone number is given from the control unit 11, the mask control circuit 21 searches the correspondence table to obtain ON / OFF information, and applies EC to the electrode of the segment to be turned on among the four segments by applying a voltage. A specific mask pattern is set on the plate 17h. The mask pattern thus set diminishes or shields the above-described leaked light.

Then, the contents of the correspondence table are registered based on measurements performed in advance. For example, the following operation program is added to the initial operation program (operation program at startup) of the control unit 11. That is, reading of predetermined information recorded in each zone of the optical disc is performed by:
This is performed while changing the mask pattern of the EC plate 17h.
Furthermore, for each mask pattern in each zone, the ratio of the level of the leak signal to the level of the recording signal (signal ratio)
Ask for. Then, the ON / OFF information of the mask pattern having the smallest signal ratio in each zone is stored in the correspondence table in association with each zone number. The mask control circuit 21 can recognize the optimum mask pattern for each zone of the optical disk from the correspondence table created as described above. The control unit 11 can also register this correspondence table by evaluating the waveform characteristics of the reproduced signal without obtaining the signal ratio.

Therefore, according to the mask pattern set on the EC board 17h based on the correspondence table, the level of the leakage signal can be reliably suppressed. The correspondence table is performed every time the optical disk is loaded, and thus has a content suitable for each optical disk. That is, according to the first embodiment, it is possible to perform reproduction corresponding to each optical disk and each area of the optical disk.

If the correspondence between the claims and the optical disk drive 1 shown in FIG.
1, corresponding to the optical pickup 17 and the reproducing circuit 13, the spatial filter corresponds to the EC board 17h, and the controller corresponds to the control unit 11 and the mask control circuit 21. <Second Embodiment> Next, a second embodiment according to the present invention will be described.
A description will be given based on FIGS. 1, 4, and 5.

FIG. 4 is a diagram showing a main configuration of the optical disk drive device 2. Here, only the differences from the optical disk drive device 1 shown in FIG. 1 will be described, and the other description will be omitted. In FIG. 4, unlike the optical disk drive 1 shown in FIG. 1, the glass plate 1 is used as a spatial filter.
7 m are arranged. Further, a slide mechanism 22 that slides the glass plate 17m in a predetermined direction is provided instead of the mask control circuit 21.

FIG. 5 is a view for explaining the structure of the glass plate 17m. The glass plate 17m is formed of a parallel plane glass having a parallel plane in a vertical section of the reflected beam. In the longitudinal direction of the parallel plane, different mask patterns are formed, and regions S1 having the same size as the cross section of the reflected beam are arranged. In FIG. 5, a hatched portion is a mask region, and a non-hatched portion is a transmission region.

The sliding mechanism 22 slides the glass plate 17m in the longitudinal direction to insert any one of the regions S1 into the cross section of the reflected beam, or to slide the glass plate 17m.
m can be retracted from the cross section of the reflected beam. When receiving the reproduction command from the host computer, the control unit 11
The zone number to which the recording track on the optical disc to be reproduced belongs is given to the slide mechanism 22.

The slide mechanism 22 has a correspondence table in which a zone number and a width (slide width) to be slid from a predetermined position in order to set a mask pattern suitable for the zone are associated. Is registered in advance. The contents of the correspondence table can be registered by measurement as in the first embodiment. When the zone number is given from the control unit 11, the slide mechanism 22 searches the correspondence table, and moves the glass plate 1 from a predetermined position by a predetermined slide width.
The optimum mask pattern is inserted into the cross section of the reflected beam by moving 7 m.

Therefore, according to the second embodiment, as in the first embodiment, reproduction corresponding to each area of an individual optical disk can be performed. In addition, if the claim and the corresponding relationship with the optical disk drive device 1 shown in FIG.
The reproduction system includes a control unit 11, an optical pickup 17, and a reproduction circuit 1.
3, the spatial filter corresponds to the glass plate 17m, and the controller corresponds to the control unit 11 and the slide mechanism 22.

Each mask region of the glass plate 17m is formed by depositing chromium on a parallel plane. An anti-reflection coating is applied to the surface of the parallel flat glass and the surface of the chromium vapor deposition portion so as not to give noise to other light receiving systems and emission systems of the optical pickup 13.
At the boundary between the mask area and the transmission area of the glass plate 17m,
A gradation of transmittance may be provided to suppress the occurrence of diffracted light at the edge of the mask region.

In the above embodiments, measurement is performed for each optical disc in order to determine how to change the mask pattern. However, the following may be performed without performing the measurement. On each optical disk, disk information indicating the type of the optical disk (for example, a manufacturer) and the type of the recording format is written. This disk information is used.

For example, after the control unit loads the optical disc,
The format information is referred to from the disc information on the optical disc. The mask control circuit or the slide mechanism has a correspondence table corresponding to each recording format, and uses only the correspondence table suitable for the recording format of the actually loaded optical disk from among them during reproduction. Alternatively, a correspondence table corresponding to the type of each optical disc may be prepared in the mask control circuit or the slide mechanism, and the control unit may use a correspondence table suitable for the type of the optical disc. Further, by preparing a correspondence table corresponding to the combination of the type of the optical disk and the type of the recording format, the optical disk drive can be more flexibly adapted to the optical disk.

In addition, the recording method of the optical disc includes land and land.
There is a groove recording method. In information reproduction from an optical disk to which this method is applied, the manner of incidence of leaked light on a reflected beam differs depending on whether a recording track to be reproduced is a land or a groove. In this case, a correspondence table for the land portion and a correspondence table for the groove portion may be created. The optical disc drive device determines whether the target recording track is a land portion or a groove portion each time reproduction is performed, and uses a correspondence table for a land portion or a groove portion according to the determination result.

In each of the above embodiments, the position where the EC plate 17h or the glass plate 17m as a spatial filter is disposed may be anywhere on the optical path of the reflected beam. For example, the condenser lens 17f and the photodetector 1 shown in FIG.
7g. Since the reflected beam passing through this optical path is condensed, the mask pattern is appropriately reduced according to the size of the cross section of the condensed reflected beam.

Further, in each of the above embodiments, the surface on which the transmission region and the mask region of the spatial filter are formed,
It does not have to be perpendicular to the optical axis of the reflected beam. In this case, the mask pattern may be deformed according to the intersection angle between the surface and the optical axis. Furthermore, if the inclination of this surface is sufficiently set, stray light generated in the optical pickup can be suppressed by removing reflected light from the spatial filter from the optical path. As a result, it is possible to suppress a tracking or focus error signal and an adverse effect on emitted light.

In each of the above embodiments, the mask pattern set in the spatial filter may be other than those shown in FIGS. Further, the type of the mask pattern may be further increased to improve the accuracy of the level suppression of the leak signal. Incidentally, when the EC plate is used as in the first embodiment, the number of segments in the cross section of the reflected beam may be increased to increase the degree of freedom in changing the mask pattern.

In each of the above embodiments, the change of the transmittance of the mask area in the spatial filter is not mentioned, but the transmittance of the mask area may be changeable. Further, the combination of the mask pattern itself and the transmittance may be changed to improve the accuracy of suppressing the level of the leak signal.
Incidentally, when the EC plate is used as in the first embodiment, the segments forming the single mask region may be further subdivided. Even in the same mask area, every other small segment is turned on,
When the entire segment is turned on, the transmittance of the entire mask area is different. By using this principle, mask patterns having different transmittances can be set.

In each of the above embodiments, the type of the optical disk is not mentioned, but the presence or absence of a recording mark is determined by the intensity of the reproduction beam reflected light or the reproduction beam, such as a phase modulation type optical disk, a phase change type optical disk, and a magneto-optical disk. If it is detected by the intensity of a specific component of the reflected light,
The present invention can be similarly applied to any optical disk drive device.

In each of the above embodiments, the setting of the mask pattern is performed so as to be adapted to the individual optical disc or the area to be reproduced on the optical disc. However, it is possible to eliminate variations in the manufacture of the disc drive device. . The optical disk drive device is provided with an optical system as shown in FIGS. If the aberration of this optical system is different, the way of imaging light is different. That is, the amplitude distribution of the leaked light in the cross section of the reflected beam optical path is different. Therefore, even when information is reproduced from the same area of the same optical disk, the quality of the reproduced signal may differ depending on the optical disk drive device.

However, in each of the above embodiments, the optical disk drive individually creates a correspondence table relating to the change of the mask pattern. That is, the contents registered in the correspondence table are specific to the optical disk drive. Therefore, if the degree of freedom in changing the mask pattern is made sufficiently high to cope with the variation in aberration of the optical disk drive device,
This problem can be solved.

Needless to say, depending on the optical disk or an area on the optical disk, when a spatial filter is not necessary (for example, the interval between adjacent tracks is sufficient, and a reproduced signal obtained from a target recording track is not necessary). In some cases, no leakage signal is mixed in the data. In the first embodiment, all the segments of the EC plate are turned off, and in the second embodiment, the glass plate is retracted from the reflected beam optical path by increasing the slide width.

[0047]

As described above, according to the first to seventh aspects of the present invention, the function of the spatial filter can be changed according to the type of the recording medium or the area to be reproduced on the recording medium. . Therefore, it is possible to reliably suppress the leakage light mixed into the reflected light, and to always obtain a good reproduction signal.

According to the third aspect of the present invention, reproduction corresponding to the type of recording medium and recording format can be performed. According to the fourth aspect of the present invention, it is possible to perform reproduction corresponding to the radial position of the area to be reproduced on the optical disc. According to the fifth aspect of the present invention, it is possible to perform reproduction corresponding to a difference between an area to be reproduced on the optical disc and a land or a groove.

According to the invention described in claim 6, it is possible to perform reproduction corresponding to the aberration of the optical system provided in the information reproducing apparatus. According to the seventh aspect of the present invention, since the setting of the spatial filter is performed based on the measurement by the apparatus itself, it is possible to cope with both the manufacturing variation of the apparatus and the optical disc.

Therefore, in the information reproduction from the current recording medium, the reproduction reliability can be improved. Furthermore, in reproducing information from a recording medium on which information is recorded at a higher density than a current recording medium, the reliability of reproduction can be ensured.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main configuration of an optical disk drive device 1;

FIG. 2 is a diagram illustrating a configuration of an EC plate 17h.

FIG. 3 is a diagram showing a mask pattern formed on an EC plate 17h.

FIG. 4 is a diagram illustrating a main configuration of an optical disk drive device 2;

FIG. 5 is a diagram illustrating a configuration of a glass plate 17m.

FIG. 6 is a diagram for explaining information reproduction by a current optical disk drive device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk drive device 13 Reproduction circuit 15 Recording circuit 17 Optical pickup 17a Semiconductor laser 17b Collimator lens 17c Mirror 17d Objective lens 17e, 17i Beam splitter 17f Condensing lens 17g Photodetector 17j Lens unit 17k Detector 17h EC board 17h1-17h4 Segment 17m Glass plate 19 Servo mechanism 21 Mask control circuit 22 Slide mechanism

Claims (7)

[Claims] 1. A reproducing system for reproducing information based on a reflected light of a reproducing beam applied to a recording medium, wherein the reproducing system is arranged in an optical path of the reflected light and can change a transmittance and / or a shape of a mask area. An information reproducing apparatus comprising: a spatial filter; and a controller that sets a light transmission state in a cross section of the optical path by changing a transmittance and / or a shape of the mask region. 2. A reproducing system for reproducing information on the basis of reflected light of a reproducing beam applied to a recording medium, wherein the reproducing system can individually insert the reflected light into an optical path and mutually transmit and receive the transmittance of a mask area. And / or a plurality of spatial filters having different shapes, and a controller configured to set a light transmission state in a cross section of the optical path by inserting one of the plurality of spatial filters into the optical path of the reflected light. An information reproducing apparatus characterized in that: 3. The information reproducing apparatus according to claim 1, wherein the controller performs the setting according to a type and / or recording format of the recording medium. 4. The information reproducing apparatus according to claim 1, wherein the recording medium is an optical disk, and the controller is configured to radiate the reproduction beam on the optical disk. An information reproducing apparatus, wherein the setting is performed according to a position. 5. The information reproducing apparatus according to claim 4, wherein the optical disk is a recording medium to which a land / groove recording method is applied, and wherein the controller is configured such that an irradiation position of the reproduction beam on the optical disk is a land. An information reproducing apparatus, wherein the setting is performed in accordance with a difference between a unit and a groove unit. 6. The information reproducing apparatus according to claim 1, wherein the content of the setting by the controller is determined in advance according to an aberration of an optical system provided in the reproducing system. An information reproducing apparatus, characterized in that: 7. The information reproducing apparatus according to claim 1, wherein the controller evaluates a quality of a reproduction signal obtained by the reproduction system, and sets the setting based on a result. An information reproducing apparatus characterized in that the information is reproduced.