Abstract:
An optical recording medium for performing a hologram recording on a first layer and a ROM reproducing layer or a thermal recording layer and easily detecting the recording location of a hologram without reducing a recording capacity. The optical recording medium includes one surface having a hologram recording layer for recording information of an object beam as interference fringes by irradiating the object beam and a reference beam and at least one other surface having a ROM layer or a thermal layer on which pits are formed to store information to easily detect the recorded location of the hologram.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the priority of Japanese Patent Application No. 2004-65841, filed on Mar. 9, 2004 in the Japanese Intellectual Property Office, and Korean Patent Application No. 2004-79210, filed on Oct. 5, 2004 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a recording medium, and more particularly, to an optical recording medium having both a hologram recording layer on which data is recorded as interference fringes by using an object beam and a reference beam and a conventional optical recording layer.  
         [0004]     2. Description of the Related Art  
         [0005]     A rewritable optical disk of a phase shift type or an optical magnetic type is widely used as an information recording medium. In order to increase the recording density of such an optical disk, the diameter of a beam spot needs to be reduced and the distance between adjacent tracks or adjacent bits needs to be made smaller. Although the recording density of an optical disk has been increased, the recording density of an optical disk is physically limited by a diffraction limit of a beam for recording data on a recording surface of the optical disk. Accordingly, a three dimensional multi-recording including a depth direction is required to increase the recording density of an optical disk.  
         [0006]     A hologram recording medium having a large capacity due to a three dimensional multi-recording region and that can be used at a high speed due to a two dimensional recording/reproducing method has attracted public attention as a next generation of computer recording media. Such a hologram recording medium may be formed by inserting a recording layer formed of a photopolymer, between two sheets of glass. In order to record data on the hologram recording medium, an object beam and a reference beam corresponding to data to be recorded are irradiated to the hologram recording medium to form interference fringes. In order to reproduce data from the hologram recording medium, a reference beam is irradiated to the interference fringes to extract optical data corresponding to the recorded data.  
         [0007]     Since a plurality of two dimensional data are recorded in the same region, the hologram recording medium formed in the same shape as a compact disk has a huge recording density on the order of tera-bytes. On the other hand, this type of medium requires very precise control of an optical system when performing multi-recording thereon in order to accurately detect locations on the medium. Thus, Japanese Laid-open Patent No. 10-124872 discloses a technology related to arranging address information on a hologram recording medium. However, when using this technology, a region for recording location information (i.e., address data or information) and a data region are formed on the same surface so that it is impossible to perform a hologram multi-recording on a recording surface and a recording capacity is reduced.  
       SUMMARY OF THE INVENTION  
       [0008]     Aspects of the present invention provide an optical recording medium that allows hologram recording and data reproducing on and from a recording surface thereof, such that a recording location of a hologram can be conveniently detected without reducing a recording capacity.  
         [0009]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
         [0010]     According to an aspect of the present invention, there is provided an optical recording medium including one surface having a hologram recording layer for recording information of an object beam as interference fringes by irradiating the object beam and a reference beam and other surface having a ROM layer in which concave or convex pits are formed.  
         [0011]     In an aspect of the present invention, optional information is recorded as ROM information on the hologram recording medium without reducing a recording capacity thereof, and a location determination control may be performed precisely.  
         [0012]     In an aspect of the present invention, the ROM layer has location information of the optical recording medium.  
         [0013]     In an aspect of the present invention, the location information is preliminarily recorded as ROM information on the hologram recording medium without reducing the hologram recording capacity, and thus an access to a predetermined address can be performed precisely and promptly when performing hologram recording/reproducing.  
         [0014]     In an aspect of the present invention, the surface having the ROM layer is formed of a ROM type optical disk.  
         [0015]     In an aspect of the present invention, it is possible to record the optional information on the ROM layer, and the access to a predetermined address can be performed precisely and promptly by using the address information of the ROM type optical disk when performing the hologram recording/reproducing.  
         [0016]     According to another aspect of the present invention, there is provided an optical recording medium including one surface having a hologram recording layer for recording information of an object beam as interference fringes by irradiating the object beam and a reference beam and other surface having a thermal recording layer.  
         [0017]     In an aspect of the present invention, optional information is additionally recorded on a hologram recording medium without reducing a hologram recording capacity by performing a thermal recording.  
         [0018]     In an aspect of the present invention, the thermal recording layer has concave or convex grooves.  
         [0019]     In an aspect of the present invention, the location of an optical system is precisely determined by controlling the optical system to move along the concave or convex grooves.  
         [0020]     In an aspect of the present invention the distance between the concave or convex grooves may be equal to a divisor of a hologram shift amount of a shift multi-recording in a perpendicular direction of the concave or convex grooves.  
         [0021]     In an aspect of the present invention, since the distance between the concave or convex grooves is determined by the divisor of the hologram amount of the shift multi-recording, it is possible to control the shift amount over the total area of the optical recording medium when performing the hologram multi-recording by moving the optical system along the grooves.  
         [0022]     In an aspect of the present invention, the thermal recording layer has location information of the optical recording medium.,  
         [0023]     In an aspect of the present invention, the location information is recorded on the hologram recording medium without reducing a hologram recording capacity, thus an access to a predetermined address may be precisely and promptly controlled when performing hologram recording/reproducing.  
         [0024]     In an aspect of the present invention, the surface having the thermal recording layer is formed of a recordable optical disk.  
         [0025]     In an aspect of the present invention, optional information is recorded on the thermal recording layer, and the access to a predetermined address may be precisely and promptly performed when performing the hologram recording/reproducing by using address information of the recordable optical disk.  
         [0026]     In an aspect of the present invention, the optical recording medium includes a total reflection layer interposed between the hologram recording layer and the ROM layer.  
         [0027]     In an aspect of the present invention, it is possible to perform recording/reproducing without interference between a hologram recording layer signal and a ROM layer signal.  
         [0028]     In an aspect of the present invention, the optical recording medium includes a total reflection layer interposed between the hologram recording layer and the thermal recording layer.  
         [0029]     In an aspect of the present invention, it is possible to perform recording/reproducing without interference between a hologram recording layer signal and a thermal recording layer signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0031]      FIGS. 1A and 1B  area sectional view and a plane view, respectively, of an optical recording medium according to an embodiment of the present invention;  
         [0032]      FIG. 2  is a sectional view of an optical recording medium according to another embodiment of the present invention;  
         [0033]      FIGS. 3A and 3B  are a sectional view and a plane view, respectively, of an optical recording medium according to another embodiment of the present invention; and  
         [0034]      FIG. 4  is a block diagram of a recording and/or reproducing apparatus according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0035]     Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
         [0036]     Referring to  FIGS. 1A and 1B , an optical recording medium  1  according to an embodiment of the present invention includes a substrate  2 , a hologram recording layer  3 , a total reflection layer  4 , a protective layer  5 , a coat layer (not shown), an adherence layer (not shown), and a substrate  6  having pits  7 . The sectional view shown in  FIG. 1A  of the optical recording medium  1  is taken along the line A-A′ of the plane view shown in  FIG. 1B . The optical recording medium  1  includes both the hologram recording layer  3  and an optical recording layer comprised of the substrate  6  having the pits  7 .  
         [0037]     Location information of the optical recording medium  1  is recorded in the pits  7 , and a location for recording a hologram or the location of a recorded hologram may be detected by optically reading with an optical pickup of a recording and/or reproducing apparatus the location information of the optical recording medium  1  from the substrate  6 . The information recorded in a ROM unit of the optical recording layer includes optional information other than the location information according to an aspect of the present invention. For instance, the ROM unit could include copy protection data and/or user data.  
         [0038]     The ROM unit may be formed of a ROM type optical disk, for example, a CD-ROM or a DVD-ROM. In this case, the location information for recording a hologram or the recorded hologram may be obtained from the address information of the CD-ROM or the DVD-ROM.  
         [0039]     The holographic recording layer  3  uses photosensitive material, such as a photopolymer or photorefractive crystal, to record interference patterns caused by an object beam and a reference beam. The object beam includes data or other information. In order to reproduce data from the hologram recording medium, a reference beam is irradiated to the interference fringes to extract optical data corresponding to the recorded data. In addition, the total reflection layer  4  reflects the object beam and the reference beam, which are irradiated to the hologram recording layer  3  from a holographic recording and/or reproducing apparatus (not shown), and prevents the object beam and the reference beam from reaching the ROM unit and thus corrupting the data or information stored in the ROM unit. Accordingly, the hologram recording layer  3  and the ROM unit may be optically separated by the total reflection layer  4 . Thus the object beam and the reference beam cannot interfere with a detection beam from, for example, an optical pickup such as that shown in  FIG. 4 , which detects location detection information arranged in a concave shape or a convex shape on the ROM unit. As a result, recording and reproducing data of high quality may be performed with the optical recording medium  1  when used with a recording and/or reproducing apparatus.  
         [0040]     Referring to  FIG. 2 , an optical recording medium  1  according to another embodiment of the present invention includes a substrate  2 , a hologram recording layer  3 , a total reflection layer  4 , a protective layer  5 , a coat layer (not shown), an adherence layer (not shown), a thermal recording layer  8 , and a substrate  9 .  
         [0041]     The location information of the optical recording medium  1  is recorded on the thermal recording layer  8  by a recording and/or reproducing apparatus illustrated in  FIG. 4 . Thus the location information is optically read by an optical pickup from the substrate  9  and the location for a recording hologram and the location of a recorded hologram are determined. The location information may be recorded in a hologram recording operation or may be preliminarily recorded. In addition, the thermally recorded information may include additional information other than the location information.  
         [0042]     The total reflection layer  4  prevents an object beam and a reference beam from reaching the thermal recording layer  8 . The object beam and reference beam record interference patterns in the hologram recording layer  3 . The object beam includes data or other information, such that during reproduction of the data from the hologram recording medium, a reference beam is irradiated to the interference fringes to extract optical data corresponding to the recorded data. Accordingly, the hologram recording layer  3  and the thermal recording layer  8  may be completely separated by the total reflection layer  4 , and thus the object beam and the reference beam cannot reach and interfere with or cause errors to an optical system, such as an optical pickup used to read the optical recording layer of the optical recording medium  1 , when the location information from the thermal recording layer  8  is read or the location information is recorded on the thermal recording layer  8 . As a result, recording and reproducing data of high quality may be performed using the optical recording medium  1 .  
         [0043]     Referring to  FIGS. 3A and 3B , an optical recording medium  1  according to another embodiment of the present invention includes a substrate  2 , a hologram recording layer  3 , a total reflection layer  4 , a protective layer  5 , a coat layer (not shown), an adherence layer (not shown), a thermal recording layer  10 , a substrate  11  having concave or convex grooves  12 . The sectional view shown in  FIG. 3A  of the optical recording medium  1  is taken along the line B-B′ of the plane view shown in  FIG. 3B .  
         [0044]     In this case, location information of the optical recording medium  1  is recorded on the thermal recording layer  10 , and the location for recording a hologram or the location of a recorded hologram may be detected by optically reading the location information of the optical recording medium  1  from the substrate  11 . The location information may be recorded in a hologram recording operation or may be preliminarily recorded. In addition, the thermally recorded information may include information other than the location information. It is understood that the recording and/or reproducing operations with respect to the thermal recording layer  10  may be performed by a recording and/or reproducing apparatus including an optical pickup such as that shown in  FIG. 4 . Also, wobble signals may be used to form the grooves.  
         [0045]     The thermal recording layer may be formed of a recording optical disk, for example, CD-R/RW or DVD±R/W type of optical recording disks. In this case, the location for recording the hologram or the location of the recorded hologram may be obtained from address information of the CD-R/RW or DVD±R/W. It is understood that other types of optical disks may be used such as advanced optical disks (AOD) or Blu-ray discs.  
         [0046]     The distance D of the grooves  12  is equal to a divisor of a shift amount when performing a shift multi-recording of a hologram in an X-direction. For example, when the shift amount is 12 μm, the distance D is 1, 2, 3, 4, 6, or 12 μm.  
         [0047]     When the distance D is 12 μm, a detection optical system is controlled to move along the grooves, thus a recording and/or reproducing optical system is automatically moved by the shift amount in the X-direction. This situation refers to the case where the detection optical system of detecting the location information and the recording and/or reproducing optical system of the recording hologram are moved integrally or in a connected state. In addition, when the distance D is 3 μm, the recording and/or reproducing optical system is moved by the shift amount in the X-direction by skipping four grooves when moving the detection optical system.  
         [0048]     While not specifically so limited, it is understood that the information storage medium  1  can include the CD-Rs, CD-RWs, DVD-RWs, DVD-RAMs, DVD+RWs, as well as next generation high definition DVDs, such as Blu-ray discs and Advanced Optical Discs (AODs).  
         [0049]      FIG. 4  is a block diagram of a recording apparatus according to an embodiment of the present invention. Referring to  FIG. 4 , the recording apparatus includes a recording/reading unit  1001 , a controller  1002 , and a memory  1003 . The recording/reading unit  1001  records data on an optical recording medium  1 , which is an embodiment of the present invention, and reads the data from the optical recording medium  1 . The controller  1002  records and reproduces optical recording medium related data according to the present invention as set forth above in relation to  FIGS. 1 through 3 B.  
         [0050]     While not required in all aspects, it is understood that the controller  1002  can be a computer implementing the method using a computer program encoded on a computer readable medium. The computer can be implemented as a chip having firmware, or can be a general or special purpose computer programmable to perform the method.  
         [0051]     In addition, it is understood that, in order to achieve a recording capacity of several dozen gigabytes on the optical recording layer, the recording/reading unit  1001  could include a low wavelength, high numerical aperture type unit usable to record dozens of gigabytes of data on the optical recording medium  1 . Examples of such units include, but are not limited to, those units using light wavelengths of 405 nm and having numerical apertures of 0.85, those units compatible with Blu-ray discs, and/or those units compatible with Advanced Optical Discs (AOD). The recording/reading unit  1001  is also capable of producing the object and reference beams for creating and/or reading the interference fringes in the hologram layer.  
         [0052]     Accordingly, a hologram recording and/or reproducing and a ROM recording and/or reproducing or a thermal recording and/or reproducing can be performed on a single optical recording medium, and the recording location of a hologram on a hologram recording layer can be easily detected.  
         [0053]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.