Patent Application
20070258344
The invention relates to multi-layer optical data storage disks and, more particularly, techniques for accessing the multiple layers of multi-layer optical data storage disks.
Optical data storage disks have gained widespread acceptance for the storage, distribution and retrieval of large volumes of information. Optical data storage disks include, for example, audio CD (compact disc), CD-R (CD-recordable), CD-RW (CD-rewritable) CD-ROM (CD-read only memory), DVD (digital versatile disk or digital video disk), DVD-RAM (DVD-random access memory), and various other types of writable or rewriteable media, such as magneto-optical (MO) disks, phase change optical disks, and others. Some newer formats for optical data storage disks are progressing toward smaller disk sizes and increased data storage density. For example, some new media formats boast finer track pitches and increased storage density using blue-violet wavelength lasers for data readout and/or data recording. Examples of blue disk media include Blu-Ray and HD-DVD.
Optical data storage disks are typically produced by first making a data storage disk master that has a surface pattern that represents encoded data on the master surface. The surface pattern, for instance, may be a collection of grooves or other features that define master pits and master lands, e.g., typically arranged in either a spiral or concentric manner. The master is typically not suitable as a mass replication surface with the master features defined within an etched photoresist layer formed over a master substrate.
After creating a suitable master, that master can be used to make a stamper, which is less fragile than the master. The stamper is typically formed of electroplated metal or a hard plastic material, and has a surface pattern that is the inverse of the surface pattern encoded on the master. An injection mold can use the stamper to fabricate large quantities of replica disks. Also, photopolymer replication processes, such as rolling bead processes, have been used to fabricate replica disks using stampers. In any case, each replica disk may contain the data and tracking information that was originally encoded on the master surface and preserved in the stamper. The replica disks can be coated with a reflective layer and/or a phase change layer, and are often sealed with an additional protective layer.
In some cases, optical data storage disks may comprise multi-layer optical disks that include two or more layers of data and tracking information. In order to access each of the layers of the multi-layer optical data storage disk, a conventional optical device must pass over the optical disk multiple times wherein the focus offset selects which layer is to be addressed. For example, the optical device must pass over a dual-layer optical data storage disk twice in order to sequentially focus a light beam of a suitable intensity onto each of the two layers.
In general, the invention is directed to techniques for simultaneously accessing multiple layers of an optical data storage medium using optical elements. In particular, the techniques include passing light through one or more optical elements included in an optical device to generate multiple light beams with focus points on two or more layers of a multi-layer optical disk. In other words, each of the multiple light beams generated by passing light through the one or more optical elements has a focus point on one of the multiple layers of the optical disk. In some cases the optical device may include a single optical element that generates multiple light beams by passing light through the optical element. In other cases, the optical device may include two or more optical elements that each generates a single light beam by passing light through the respective elements. In either case, the optical device may simultaneously access two or more of the layers of the optical disk in a single pass.
An optical element according to the invention may comprise a diffractive optical element (DOE) or a holographic optical element (HOE). In some cases, one or more optical elements may be positioned adjacent a refractive element, such as an objective lens, within an existing optical device. In other cases, one or more optical elements may be combined with a refractive lens to form a new optical device. The resulting optical device may be utilized within a phase change initialization system or as a read head within a disk drive.
An optical element, as described herein, may be designed to accommodate the separation distance between each of the layers of a multi-layer optical disk and a power ratio for the layers of the multi-layer optical disk. Most of the multi-layer optical data storage medium formats have uniform layer separation distances. However, some multi-layer optical data storage medium formats may have non-uniform layer separation distances. In some cases, the power levels may be substantially constant for each of the multiple layers of the optical disk. In other cases, the power levels may vary significantly for the multiple layers of the optical disk. In this way, the optical element may generate one or more light beams with focus points on each of the layers and with appropriate intensity levels such that the power delivered to each of the layers meets a predetermined level. The term “intensity” is defined herein to mean power per unit area of a beam of light.
In one embodiment, the invention is directed to a method comprising generating multiple light beams by passing light through one or more optical elements. The method also comprises simultaneously accessing two or more layers of an optical data storage disk with the multiple light beams, wherein each of the multiple light beams has a focus point on one of the two or more layers of the optical data storage disk.
In another embodiment, the invention is directed to a system comprising an optical data storage disk including two or more layers, and an optical device including one or more light sources and one or more optical elements. The light sources pass light through the optical elements to generate multiple light beams, wherein each of the multiple light beams has a focus point on one of the two or more layers of the optical data storage disk to simultaneously access the two or more layers of the optical data storage disk.
In a further embodiment, the invention is directed to a method comprising determining separation distances between two or more layers of an optical data storage disk, and determining power ratios for the two or more layers of the optical data storage disk. The method also comprises creating an optical element that generates one or more light beams from an initial light beam, wherein each of the one or more light beams has a focus point on one of the two or more layers of the optical data storage disk based on the layer separation distances and the power ratios.
The invention may be capable of providing one or more advantages. For example, the described techniques may substantially increase production process throughput for initialization of multi-layer rewritable optical disks by initializing the multiple layers simultaneously. In the case of a dual-layer optical disk, for example, the techniques may double the production process throughput. In the case of a four-layer optical disk, the techniques may quadruple the production process throughput. Similarly, the techniques may substantially increase readout data rate for a read head of a disk drive when reading data stored on a multi-layer optical disk by reading data from the multiple layers simultaneously.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
The invention is directed to techniques for simultaneously accessing multiple layers of an optical data storage medium using optical elements. In particular, the techniques include passing light through one or more optical elements included in an optical device to generate multiple light beams with focus points on each layer of a multi-layer optical disk. In other words, each of the multiple light beams generated by the one or more optical elements has a focus point on one of the layers of the optical disk. In some cases the optical device may include a single optical element that generates multiple light beams by passing light through the optical element. In other cases, the optical device may include two or more optical elements that each generates a single light beam by passing light through each of the optical elements. In either case, the optical device may simultaneously access two or more of the layers of the optical disk in a single pass.
An optical element may comprise a diffractive optical element (DOE) or a holographic optical element (HOE). In some cases, one or more optical elements may be positioned adjacent a refractive element, such as an objective lens, within an existing optical device. In other cases, one or more optical elements may be combined with a refractive lens to form a new optical device. For example, the optical device may be utilized within a phase change initialization system, or as a read head within a disk drive.
In the case of a phase change initialization system, the techniques described herein enable the optical device to simultaneously initialize phase change recording material applied over multiple layers included in a rewritable optical data storage disk for data recording. The optical device provides focus points of multiple light beams to simultaneously access the layers of the multi-layer optical disk and alter the phase change recording material on the layers. In the case of a read head, the techniques described herein enable the optical device to simultaneously readout data stored on each layer of a multi-layer optical data storage disk. The optical device provides focus points of multiple light beams to simultaneously access the layers of the multi-layer optical disk and the layers, in turn, simultaneously reflect the multiple light beams back to the read head for readout of the layers. In either case, the optical device sweeps over the optical disk only once while providing focus points of multiple light beams generated by at least one optical element on two or more layers of the optical disk.
An optical element, as described herein, may be designed to accommodate the separation distance between each of the layers of a multi-layer optical disk and a power ratio for the layers of the multi-layer optical disk. Most standard multi-layer optical data storage medium formats have uniform layer separation distances. However, some multi-layer optical data storage medium formats may have non-uniform layer separation distances. For example, a dual-layer Blu-Ray optical disk has a layer separation of approximately 25 μm, and a dual-layer DVD or HD-DVD has a layer separation of approximately 55 μm. In this way, the optical element may generate one or more light beams with focus points on each of the layers. In other cases, a multi-layer optical data storage medium format may have non-uniform layer separation. For example, a four-layer optical disk may have separation distances of 10, 25 and 35 μm respectively between each of the successive layers.
Each of the layers of the optical disk defines a minimum intensity level required to access, e.g., initialize or read, the layer. The term “intensity” is defined herein to mean power per unit area of a beam of light. In some cases, each of the layers may require substantially equivalent intensity levels. In other cases, each of the layers may require a different intensity level. The power ratio for the layers of the multi-layer optical disk may be determined based on the intensity level for each of the multiple layers. In the case of a lower layer of the optical data storage disk, an intensity level may be determined for the lower layer and for transmission through one or more upper layers of the optical data storage disk. In this way, the optical element may generate one or more light beams with appropriate intensity levels such that the power delivered to each of the layers meets a predetermined level.
As discussed above, the techniques described herein may also be applied to a variety of optical devices for optical disks with any number of layers. For example, the optical devices may be utilized within phase change initialization systems, or as read heads within disk drives. In addition, the optical disks may include two or four layers, or any other number of layers. For purposes of illustration, the techniques will be described below in reference to optical devices within initialization systems. In addition, the techniques will be applied to optical disks with either two or four layers. However, the invention should not be limited in these respects.
Multi-layer optical disk 8 may comprise a rewritable optical disk with two or more layers of data and tracking information. For example, multi-layer optical disk 8 may comprise a dual-layer optical disk with two information layers. In other cases, multi-layer optical disk 8 may comprise any number of information layers. The layers of multi-layer optical disk 8 may comprise disk-shaped polycarbonate substrates coated with a multi-layered thin-film stack including a phase change recording material. Other substrate materials of suitable optical surface quality may also be used for the two or more layers included in multi-layer optical disk 8. In addition, multi-layer optical disk 8 may include spacer material between each of the layers. Multi-layer optical disk 8 is carefully placed in system 10 on spindle 17.
In accordance with embodiments of the invention, optical device 18 includes one or more light sources and one or more optical elements. Each of the one or more optical elements may comprise a DOE or a HOE. The one or more optical elements generate multiple light beams with focus points on the two or more layers of multi-layer optical disk 8 to simultaneously initialize the layers. The multiple light beams simultaneously alter the phase change recording material coating the two or more layers of optical disk 8 according to commands by system control 12 to initialize the two or more layers for data recording. In this way, optical device 18 sweeps over multi-layer optical disk 8 only once while providing focus points of the multiple light beams generated by the at least one optical element on the two or more layers of multi-layer optical disk 8.
Spindle controller 14 causes spindle 17 to spin multi-layer optical disk 8, while optical device controller 15 controls the positioning of optical device 18 relative to optical disk 8. Optical device controller 15 also controls any on-off switching of light that is emitted from optical device 18. As multi-layer optical disk 8 spins on spindle 17, optical device controller 15 translates optical device 18 to desired positions and causes optical device 18 to emit the multiple light beams to simultaneously initialize the two or more layers of multi-layer optical disk 8.
The described techniques may substantially increase production process throughput for initialization of multi-layer rewritable optical disk 8 by initializing the multiple layers simultaneously. As an example, in the case of a dual-layer optical disk, the techniques may double the production process throughput.
In the illustrated embodiment, dual-layer optical disk 8A comprises a rewritable dual-layer optical disk. Therefore, first layer 32 and second layer 36 of dual-layer optical disk 8A are coated with a multi-layer thin-film stack including a phase change recording material that must be initialized for data recording. Dual-layer optical disk 8A also includes a spacer material 34 between first layer 32 and second layer 36. As shown in
In addition, each of first layer 32 and second layer 36 of dual-layer optical disk 8A defines a minimum intensity level required to access, e.g., initialize, the layer. In other words, each of the layers 32 and 36 require a specific amount of power to alter the phase change recording material applied over the layers 32 and 36 and initialize the layers 32 and 36. In some cases, each of layers 32 and 36 may require a substantially equivalent intensity level. In other cases, each of layers 32 and 36 may require different intensity levels.
Within optical device 18A, optical element 24 is positioned adjacent refractive lens 26. In some cases, optical device 18A may comprise an existing optical device and optical element 24 may be positioned adjacent refractive lens 26 within the existing optical device. In other cases, optical device 18A may comprise a new optical device and optical element 24 may be combined with refractive lens 26 to form the new optical device.
Light source 22 passes an initial light beam through optical element 24. For example, light source 22 may pass a laser light beam with a wavelength of approximately 810 nm for initialization. In the illustrated embodiment, optical element 24 splits the initial light beam into two light beams. Refractive lens 26 then provides a first focus point 28 of the first light beam on first layer 32 of dual-layer optical disk 8A and provides a second focus point 30 of the second light beam on second layer 36 of dual-layer optical disk 8A. The two light beams have focus points 28 and 30 at specific distances along the focal axis between optical device 18A and dual-layer optical disk 8A to access layers 32 and 36, respectively. The two light beams also have a power ratio such that focus points 28 and 30 deliver appropriate intensity levels to layers 32 and 36 to meet the predetermined levels required by the layers 32 and 36.
Optical element 24 may comprise a DOE or a HOE designed based on separation distance D2 between first layer 32 and second layer 36 of dual-layer optical disk 8A and the power ratio for layers 32 and 36. In the case of a DOE, optical element 24 may include a surface relief pattern with a step grating, a blaze grating, or another type of grating. In this way, optical element 24 may generate two light beams with focus points 28 and 30 at appropriate locations and with appropriate intensity levels for the respective layers 32 and 36 of dual-layer optical disk 8A.
As shown in
For example, first layer 32 may have an intensity level requirement of approximately 1 MW/cm2 and second layer 32 may have an intensity level requirement of approximately 1.7 MW/cm2. Therefore, the first light beam with first focus point 28 may have an intensity level of 1 MW/cm2 to deliver to first layer 32. However, the second light beam with second focus point 30 on second layer 36 may have a total intensity level of between approximately 2 and 3 MW/cm2. In this way, the second light beam may lose a portion of the total power for transmission through first layer 32 and spacer material 34 of dual-layer optical disk 8A and still deliver an intensity level of 1.7 MW/cm2 to second layer 36.
Optical device 18A sweeps over dual-layer optical disk 8A only once while providing focus points 28 and 30 of the two light beams generated by optical element 24 on each of layers 32 and 36 of dual-layer optical disk 8A. In this way, optical device 18A may simultaneously initialize first layer 32 and second layer 36 by initializing the phase change recording material coated on the layers with focus points 28 and 30 of the light beams.
In the illustrated embodiment, dual-layer optical disk 8B comprises a rewritable dual-layer optical disk. Therefore, first layer 52 and second layer 56 of dual-layer optical disk 8B are coated with a multi-layer thin-film stack including a phase change recording material that must be initialized for data recording. Dual-layer optical disk 8B also includes spacer material 54 between first layer 52 and second layer 56. As shown in
In addition, each of first layer 52 and second layer 56 of dual-layer optical disk 8B defines a minimum intensity level required to access, e.g., initialize, the layer. In other words, each of the layers 52 and 56 require a specific amount of power to alter the phase change recording material applied over the layers 52 and 56 and initialize the layers 52 and 56. In some cases, each of layers 52 and 56 may require a substantially equivalent intensity level. In other cases, each of layers 52 and 56 may require different intensity levels.
Within optical device 18B, optical elements 44A and 44B are positioned adjacent refractive lens 46. In other embodiments, first optical element 44A may be positioned adjacent a first refractive lens within optical device 18B and second optical element 44B may be positioned adjacent a second refractive lens within optical device 18B. In some cases, optical device 18B may comprise an existing optical device, and first optical element 44A and second optical element 44B may be positioned adjacent refractive lens 46 within the existing optical device. In other cases, optical device 18B may comprise a new optical device, and first optical element 44A and second optical element 44B may be combined with refractive lens 46 to form the new optical device.
First light source 42A passes an initial light beam through first optical element 44A and second light source 42B passes an initial light beam through second optical element 44B. For example, light sources 42A and 42B may pass laser light beams with wavelengths of approximately 810 nm for initialization. In the illustrated embodiment, first optical element 44A generates a first light beam and second optical element 44B generates a second light beam. Refractive lens 46 then provides a first focus point 48 of the first light beam on first layer 52 of multi-layer optical disk 8B and provides a second focus point 50 of the second light beam on second layer 56 of multi-layer optical disk 8B. The two light beams have focus points 48 and 50 at specific distances along the focal axis between optical device 18B and dual-layer optical disk 8B to access layers 52 and 56, respectively. The two light beams also have a power ratio such that focus points 48 and 50 deliver appropriate intensity levels to layers 52 and 56 to meet the predetermined levels required by the layers 52 and 56.
First optical element 44A may comprise a DOE or a HOE designed based on distance D1 between optical device 18B and first layer 52 of dual-layer optical disk 8B and the intensity level for first layer 52. Second optical element 44B may comprise a DOE or a HOE designed based on separation distance D2 between first layer 52 and second layer 56 of dual-layer optical disk 8A and the intensity level for second layer 56. In the case of DOEs, each of optical elements 44A and 44B may include a surface relief pattern with a step grating, a blaze grating, or another type of grating. In this way, each of optical elements 44A and 44B may generate a single light beam with focus point 48 or 50 at an appropriate location and with an appropriate intensity level for the respective one of layers 52 and 56 of dual-layer optical disk 8B.
As shown in
Optical device 18B sweeps over dual-layer optical disk 8B only once while providing focus points 48 and 50 of the two light beams generated by optical elements 44A and 44B on each of layers 52 and 56 of dual-layer optical disk 8B. In this way, optical device 18B may simultaneously initialize first layer 52 and second layer 56 by altering the phase change recording material coated on the layers with focus points 48 and 50 of the light beams.
In the illustrated embodiment, multi-layer optical disk 8C comprises a rewritable multi-layer optical disk. Therefore, first layer 86, second layer 90, third layer 94, and fourth layer 98 of dual-layer optical disk 8C are coated with a multi-layer thin-film stack including a phase change recording material that must be initialized for data recording. Multi-layer optical disk 8C also includes spacer material 88 between first layer 86 and second layer 90, spacer material 92 between second layer 90 and third layer 94, and spacer material 96 between third layer 94 and fourth layer 98.
As shown in
In addition, each of first layer 86, second layer 90, third layer 94, and fourth layer 98 of multi-layer optical disk 8C defines a minimum intensity level required to access, e.g., initialize, the layer. In other words, each of layers 86, 90, 94, and 98 require a specific amount of power to alter the phase change recording material applied over the layers and initialize the layers. In some cases, each of layers 86, 90, 94, and 98 may require a substantially equivalent intensity level. In other cases, each of layers 86, 90, 94, and 98 may require a different intensity level.
Within optical device 18C, optical element 74 is positioned adjacent refractive lens 76. In some cases, optical device 18C may comprise an existing optical device and optical element 74 may be positioned adjacent refractive lens 76 within the existing optical device. In other cases, optical device 18C may comprise a new optical device and optical element 74 may be combined with refractive lens 76 to form the new optical device.
Light source 72 passes an initial light beam through optical element 74. For example, light source 72 may pass a laser light beam with a wavelength of approximately 810 nm for initialization. In the illustrated embodiment, optical element 74 splits the initial light beam into four light beams. Refractive lens 76 then provides a first focus point 78 of the first light beam on first layer 86, provides a second focus point 80 of the second light beam on second layer 90, provides a third focus point 82 of the third light beam on third layer 94, and provides a fourth focus point 84 of the fourth light beam on fourth layer 98. The four light beams have focus points 78, 80, 82, and 84 at specific distances along the focal axis between optical device 18C and multi-layer optical disk 8C to access layers 86, 90, 94, and 98, respectively. The four light beams also have a power ratio such that focus points 78, 80, 82, and 84 deliver appropriate intensity levels to layers 86, 90, 94, and 98 to meet the predetermined levels required by the layers.
Optical element 74 may comprise a DOE or a HOE designed based on separation distance D2 between each of layers 86, 90, 94, and 98 of multi-layer optical disk 8C and the power ratio of layers 86, 90, 94, and 98. In the case of a DOE, optical element 74 may include a surface relief pattern with a step grating, a blaze grating, or another type of grating. In this way, optical element 74 may generate four light beams with focus points 78, 80, 82, and 84 at appropriate locations and with appropriate intensity levels for the respective layers 86, 90, 94, and 98 of multi-layer optical disk 8C.
As shown in
The power ratio for layers 86, 90, 94, and 98 of multi-layer optical disk 8C may be determined based on the intensity level for each of the four layers. In the case of second layer 90, an intensity level may be determined for second layer 90 and for transmission through first layer 86 and spacer material 88 of multi-layer optical disk 8C. In the case of third layer 94, an intensity level may be determined for third layer 94 and for transmission through first layer 86, spacer material 88, second layer 90, and spacer material 92 of multi-layer optical disk 8C. In the case of fourth layer 98, an intensity level may be determined for fourth layer 98 and for transmission through first layer 86, spacer material 88, second layer 90, spacer material 92, third layer 94, and spacer material 96 of multi-layer optical disk 8C.
Optical device 18C sweeps over multi-layer optical disk 8C only once while providing focus points 78, 80, 82, and 84 of the four light beams generated by optical element 74 on each of layers 86, 90, 94, and 98 of dual-layer optical disk 8C. In this way, optical device 18C may simultaneously initialize first layer 86, second layer 90, third layer 94, and fourth layer 98 by altering the phase change recording material coated on the layers with focus points 78, 80, 82, and 84 of the light beams.
In each of the illustrated embodiments, the second intensity level of focus point 80 on second layer 90 of optical disk 8C may include the intensity level required by second layer 90 and the intensity level required for transmission through first layer 86 and spacer 88 of optical disk 8C. The third intensity level of focus point 82 on third layer 94 of optical disk 8C may include the intensity level required by third layer 94 and the intensity level required for transmission through first layer 86, spacer 88, second layer 90, and spacer 92 of optical disk 8C. The fourth intensity level of focus point 84 on fourth layer 98 of optical disk 8C may include the intensity level required by fourth layer 94 and the intensity level required for transmission through first layer 86, spacer 88, second layer 90, spacer 92, third layer 94, and spacer 96 of optical disk 8C.
First, a separation distance, D2, between first layer 32 and second layer 36 of dual-layer optical disk 8A is determined (120). Most standard multi-layer optical data storage medium formats have a uniform layer separation distance. However, some multi-layer optical data storage medium formats may have non-uniform layer separation distances. In the case where optical disk 8A comprises a dual-layer Blu-Ray optical disk, separation distance D2 may be approximately 25 μm. In the case where optical disk 8A comprises a dual-layer DVD or HD-DVD optical disk, separation distance D2 may be approximately 55 μm. In other cases, a multi-layer optical data storage medium format may have non-uniform layer separation. For example, a four-layer optical disk may have separation distances of 10, and 35 μm respectively between each of the successive layers.
Then a power ratio for first layer 32 and second layer 36 of dual-layer optical disk 8A is determined (122). Each of the layers of the optical disk defines a minimum intensity level required to initialize the layer, i.e., alter the phase change recording material coating the layer. In some cases, first layer 32 and second layer 36 may require substantially equivalent intensity levels. In other cases, first layer 32 may require a first intensity level that is higher or lower than a second intensity level required by second layer 36. For example, when determining the intensity level for second layer 36, an intensity level may be determined for second layer 36 and for transmission through first layer 32 and spacer material 34 of dual-layer optical data storage disk 8A.
Optical element 24 may then be created based on the determined layer separation distance and the determined power ratio for dual-layer optical disk 8A (124). In this way, optical element 24 may generate two light beams with focus points on each of first layer 32 and second layer 36. Optical element 24 may comprise a DOE or a HOE. For example, optical element 24 may comprise a DOE including a surface relief pattern with a step grating designed to generate two light beams from an initial light beam, substantially similar to DOE 60 from
Optical element 24 may be positioned adjacent refractive lens 26 within optical device 18A (126). In some cases, optical device 18A may comprise an existing optical device and optical element 24 may be positioned adjacent refractive lens 26 within the existing optical device. In other cases, optical device 18A may comprise a new optical device and optical element 24 may be combined with refractive lens 26 to form the new optical device.
Light source 22 included within optical device 18A generates an initial light beam and passes the initial light beam through single optical element 24 (130). Optical element 24 generates two light beams from the initial light beam (132). Refractive lens 26 then provides focus points 28 and 30 of the two light beams on each of the first layer 32 and second layer 36 of dual-layer optical disk 8A (134). In other words, refractive lens 26 provides a first focus point 28 of a first light beam from optical element 24 on first layer 32 and provides a second focus point 30 of a second light beam from optical element 24 on second layer 36. Once the focus points are provided on the layers, optical device 18A may simultaneously initialize the phase change recording material coated over first layer 32 and second layer 36 of dual-layer optical disk 8A for data recording (136).
Each of light sources 42A and 42B included within optical device 18B generates an initial light beam and passes the initial light beam through a respective one of optical elements 44A and 44B (140). Each of optical elements 44A and 44B generates a single light beam from the respective initial light beam (142). Refractive lens 46 then provides focus points 48 and 50 of the two light beams on each of the first layer 52 and second layer 56 of dual-layer optical disk 8B (144). In other words, refractive lens 46 provides a first focus point 48 of a first light beam from optical device 44A on first layer 52 and provides a second focus point 50 of a second light beam from optical device 44B on second layer 56. Once the focus points are provided on the layers, optical device 18B may simultaneously initialize the phase change recording material coated over first layer 52 and second layer 56 of dual-layer optical disk 8B for data recording (146).
Various embodiments of the invention have been described. For example, techniques have been described for simultaneously accessing multiple layers of an optical data storage medium using optical elements. In one embodiment, the techniques include passing light through a single optical element included in an optical device that generates multiple light beams, where each of the multiple light beams has a focus point on one of the layers of a multi-layer optical disk. In another embodiment, the techniques include passing light through two or more optical elements included in an optical device, where each of the optical elements generates a single light beam with a focus point on one of the layers of a multi-layer optical disk. In either embodiment, each of the multiple light beams has a focus point on one of the layers of a multi-layer optical disk to simultaneously access two or more of the layers of the optical disk.
For example, the optical device may be utilized within a phase change initialization system or as a read head within a disk drive. In the case of a phase change initialization system, the techniques described herein enable the optical device to simultaneously initialize phase change recording material applied over multiple layers included in a rewritable optical data storage disk for data recording. The optical device provides focus points of multiple light beams to simultaneously access the layers of the multi-layer optical disk and alter the phase change recording material on the layers. In the case of a read head, the techniques described herein enable the optical device to simultaneously readout data stored on each layer of a multi-layer optical data storage disk. The optical device provides focus points of multiple light beams to simultaneously access the layers of the multi-layer optical disk and the layers, in turn, simultaneously reflect the multiple light beams back to the read head for readout of the layers. In either case, the optical device sweeps over the optical disk only once while providing focus points of multiple light beams generated by at least one optical element on each layer of the optical disk.
Nevertheless various modifications can be made to the techniques described herein without departing from the spirit and scope of the invention. The techniques are primarily described herein with reference to optical devices within initialization systems. In addition, the optical disks are primarily depicted as including two or four layers with substantially uniform layer separation distances. However, the techniques may be applied to other optical devices, such as read heads within disk drives, to simultaneously readout data from a multi-layer optical disk. The techniques may also be applied to optical disks with any number of layers. Furthermore, the techniques may be applied to optical disks with non-uniform layer separation distances. These and other embodiments are within the scope of the following claims.
