Techniques for storing and retrieving data using a sphere-shaped data storage structure

An optical storage system includes a frame (e.g., a rack-mount drawer), an environmental assembly (e.g., a power and cooling subsystem) supported by the frame, and a set of optical storage devices coupled to the environmental assembly. Each optical storage device has a base, a storage medium (e.g., a sphere-shaped holographic data storage structure) disposed on the base, and an optical assembly coupled to the base. The storage medium has a curved surface configured to store data in a digital manner thereon. The optical assembly is configured to optically write the data to and read the data from the curved surface of the storage medium.

BACKGROUND

Conventional holographic video storage equipment includes (i) a laser beam source, (ii) a beam splitter, (iii) a spatial light modulator, and (iv) a flat, transparent, holographic storage disk. To write data to the disk, the laser beam source emits a beam of laser light. The beam splitter separates the laser beam into a signal beam and a reference beam. The spatial light modulator encodes a data pattern within the signal beam but not into the reference beam. The signal beam and the reference beam then intersect each other at a relatively-narrow location of the holographic storage disk. Photosensitive material within the holographic storage disk reacts to the intersection of these beams and, as a result, stores the data pattern three-dimensionally as layered digital pages (i.e., a hologram) at that location.

In contrast to conventional compact disks (CDs) and digital versatile disks (DVDs) which are flat, reflective disks that reflect laser light from a laser source onto an optical reader while the disks are spinning, a flat, transparent, holographic storage disk remains stationary during the writing and reading process. Furthermore, the holographic storage disk is mainly non-reflective so that, during the reading process, light from one side of the holographic storage disk shines on a hologram within the disk (i.e., layered digital pages) and a sensor on the other side of the disk reads the refracted light to re-construct the data pattern.

Since the data pattern is capable of including several digital pages of data, a significant amount of information can be stored on a single holographic storage disk. Some companies have reported the capability of storing 2 Gigabytes (GBs) in an area of a holographic storage disk which is roughly the size of a conventional postage stamp, as well as the ability to read that data at a rate of 20 Megabits per second (Mb/s). An example of a company providing similar reports is InPhase Technologies of Longmont, Colo.

SUMMARY

Unfortunately, there are deficiencies to the above-described conventional holographic storage equipment and disks. For example, due to the flat platter geometry of the conventional holographic storage disk, there is currently a need for complex electromechanical devices to traverse relatively long travel lengths in order to access the various locations of each disk. Although data patterns can be read relatively quickly once an electromechanical device has properly positioned the data access components at a particular data storage location, there are latencies which result from moving the data access components around the disk. Furthermore, such movement can result in a substantial amount of heat build up and wear and tear thus posing a potential source of error or even failure.

In contrast to the above-described conventional holographic storage equipment and disks, improved data storage techniques involve the use of a storage medium having a curved surface (e.g., a holographic storage sphere) and an optical assembly configured to optically write data to and read data from the curved surface of the storage medium. The use of such a storage medium and optical assembly minimizes the need for extensive travel of the optical assembly. Rather, data access operations can be effectuated by simply orienting the optical assembly from a location which is substantially central to an internal space defined by the curved surface of the storage medium. Such orientation can occur with minimal latency and travel (e.g., simple control of angular direction). Accordingly, data access times are optimized, and mechanical movement and the associated heat generation are kept to a minimum.

One embodiment is directed to an optical storage system which includes a frame (e.g., a rack-mount drawer), an environmental assembly (e.g., a power and cooling subsystem) supported by the frame, and a set of optical storage devices coupled to the environmental assembly. Each optical storage device has a base, a storage medium (e.g., a sphere-shaped holographic data storage structure) disposed on the base, and an optical assembly coupled to the base. The storage medium has a curved surface configured to store data in a digital manner thereon. The optical assembly is configured to optically write the data to and read the data from the curved surface of the storage medium.

DETAILED DESCRIPTION

Improved data storage techniques involve the use of a storage medium having a curved surface (e.g., a holographic storage sphere) and an optical assembly configured to optically write data to and read data from the curved surface of the storage medium. The use of such a storage medium and optical assembly minimizes the need for extensive travel of the optical assembly. Rather, data access operations can be accomplished by simply orienting the optical assembly from a location which is substantially central to an internal space defined by the curved surface of the storage medium. Such orientation can occur with minimal time latency and travel (e.g., simple control of angular direction). Accordingly, data access times are optimized, and mechanical movement and the associated heat generation are kept to a minimum.

FIG. 1shows an optical storage system20which is configured to store data holographically. The optical storage system20includes a frame22, an environmental assembly24and a set of optical storage devices26(i.e., one or more optical storage devices26). The frame20is configured to fit within a larger support system (e.g., an equipment rack, an electronic cabinet, etc.). Accordingly, the optical storage system20is capable of joining other data storage components (e.g., other optical storage systems, mixed with standard magnetic storage systems, etc.) as part of a larger storage array which is easily scalable.

In the particular arrangement shown inFIG. 1, the frame22includes mounting hardware28and a drawer30. The mounting hardware28is configured to mount the drawer30to vertical rails of an equipment rack32, and allow a user to conveniently slide the drawer30out of the equipment rack32(e.g., for upgrading, for servicing, etc.) or slide the drawer30back in to the equipment rack32in a substantially horizontal manner. The drawer30is configured to support both the environmental assembly24and the optical storage devices26. As shown inFIG. 1, drawer30is capable of holding the optical storage devices26in a high density formation having a two-dimensional layout in the X-Y plane to provide a high memory space to physical space ratio. Accordingly, the optical storage system20is particularly well-suited for storage applications dealing with extremely large amounts of data (e.g., archives, libraries, databases, etc.).

The environmental assembly24is configured to provide a variety of resources to the set of the optical storage devices26including main power33(e.g., a set of power supply signals) and an air stream34(e.g., a set of fans) to remove heat. By way of example only, the air stream34is shown as flowing front to back so that ambient air enters through the front of the drawer30and exits through the rear. The environmental assembly24is capable of providing other resources as well such as a communications fabric36from the optical storage devices26to a controller38, battery backup power40, and so on.

Each optical storage device26is configured to store and retrieve data holographically. Such optical storage devices26are capable of replacing magnetic disk drives in a variety of contexts (e.g., in general purpose computers, in RAID arrangements, in data storage systems which perform load and store operations on behalf of external hosts, etc.). Further details will now be provided with reference toFIG. 2.

FIG. 2is a sectional view of an optical storage device26in accordance with a first embodiment. The optical storage device26includes a base50having an interface52which is configured to connect to and disconnect from the environmental assembly24in a modular manner for hot-swappability (e.g., for quick removal and installation). In some arrangements, the interface52includes electrical connectors which connect to power supply terminals to obtain power as well as a communications port to exchange data. In other arrangements, the interface52includes electrical connectors which connect to power supply terminals for power, and a wireless transceiver (illustrated generally by the reference number52inFIG. 2) for wireless data communications (e.g., data exchange with the controller38inFIG. 1).

The optical storage device26further includes a storage medium54and an optical assembly56both of which are disposed on the base50. The storage medium54has a curved surface58configured to store data in a digital manner thereon. The optical assembly56is configured to optically write the data to and read the data from the curved surface58of the storage medium54.

As shown inFIG. 2, the storage medium54includes a sphere-shaped structure60which defines an internal space62and an external space64. The BuckyBall-shape of the storage medium allows air to pass around the curved edges for enhanced cooling. The storage medium54includes photosensitive recording material which is configured to store holographic images as digital data pages. Such materials preferably are transparent, highly photosensitive, thermally stable and adaptable to reliably remain substantially in the shape of a sphere having a size which is between a golf ball and baseball. Examples of similar materials are photopolymers and photonic coatings and materials designated by the mark Tapestry® which is available from InPhase Technologies of Longmont, Colo.

The optical assembly56of the optical storage device26includes a light source66disposed within the internal space62, a light sensor68disposed within the external space64, and an actuation mechanism70. The actuation mechanism70defines a central axis72, and has a first end74which attaches to the base50and a second end76disposed at a central location78within the internal space62. The light source66attaches to the second end76and is safely sheltered from the external space64. The light source66and the light sensor68electrically connect to the interface52within the base50for power and data I/O (e.g., wireless data communications). The actuation mechanism70is configured to point the light source66toward designated data storage locations on the storage medium54. The light source66is configured to provide light during data writing and data reading operations performed on the curved surface58of the storage medium54. The light sensor68is configured to sense light from the light source66which passes through the curved surface58of the storage medium54and thus read data stored within the storage medium54.

One of ordinary skill in the art will appreciate that the actuation mechanism70is capable of relying on a simple angular displacement about the central vertical axis72(i.e., azimuth) in combination with a simple angular displacement from horizontal (i.e., altitude). Such operation enables the actuation mechanism70to aim the light sensor68at a particular data storage location of the storage medium54(i.e., a selected curved portion of the sphere-shaped structure60among multiple curved portions) based on electronic signals from a controller (e.g., see the controller38inFIG. 1). Moreover, a variety of coordinate mapping schemes are suitable for use such as X/Y grid, azimuth/altitude, longitude/latitude, and so on. Accordingly, in contrast to linear actuators of magnetic disk drives which must convey magnetic read and write heads back and forth along a lengthy radial axis of a flat magnetic disk, there is little movement linear movement of the light source66and thus minimal heat generation due to extensive mechanical actuation. Furthermore, positioning latency by the actuation mechanism70is capable of being as good as or even better than that of magnetic disk drives.

In some arrangements and as shown inFIG. 2, the light sensor68is globe-shaped and surrounds the storage medium54thus alleviating the need for a moving sensor. In these arrangements, as light passes through the storage medium54, that light is detected by a portion of the light sensor68immediately adjacent to the storage medium54. Nevertheless, there is nothing that precludes the use of a smaller light sensor68which is moved to specific locations behind the storage medium54(e.g., by the actuation mechanism70) for precise localized light sensing. Further details will now be provided with reference toFIG. 3.

FIG. 3is a general perspective view of a portion of the optical storage device26involved in data reading and data writing operations. The light source66includes a coherent laser source80, a beam splitter82, a director84, and a spatial light modulator86. The coherent laser source80is configured to provide a coherent light beam88. The beam splitter82is configured to split the coherent light beam88into a signal beam90and a reference beam92. The director84is configured to direct the reference beam92toward the curved surface58of the storage medium54. The spatial light modulator (SLM)86is configured to encode data patterns94within the signal beam90and then output an encoded signal beam96(i.e., the original signal beam90which has been modified to include the encoded data patterns94) toward the curved surface58of the storage medium54. The intersection of the reference beam92and the encoded signal beam96at the curved surface58forms a holographic interference pattern98on the storage medium54.

The light sensor68preferably includes a globe-shaped detector array100which is coupled to the base50and disposed in the external space64outside the storage medium54(also seeFIG. 2). The detector array100is configured to detect the holographic interference pattern98formed on the storage medium54by sensing light102passing through the holographic interference pattern98at the curved surface58of the storage medium54. As a result, the data patterns94are capable of being easily reconstructed.

Accordingly, during write operations, the director84directs the reference beam92and the SLM86aims the encoded signal beam96so that the reference beam92and the encoded signal beam96intersect at a targeted data storage location of the storage medium54. At this targeted location, the intersecting beams92,96form an interference pattern of bright and dark regions within the photosensitive recording material of the storage medium54thus forming, as the holographic image98within the storage medium54, a multi-page digital data pattern.

Furthermore, during read operations, light from one beam (e.g., the reference beam92from the director88) passes through the holographic image96at the targeted location. As the light passes through the holographic image98, the globe-shaped detector array100of the light sensor68receives the light and reconstructs the data pattern. Further details of the optical storage system20will now be provided with reference toFIG. 4.

FIG. 4is a top view of a particular arrangement for the optical storage devices26which is well-suited for high density storage. The optical storage devices26are positioned to form a honey-comb arrangement where the sphere-shaped storage media structure60of each internally positioned device26(e.g., the structure60(n) inFIG. 4) derives a degree of structural support from six neighboring sphere-shaped structures60. Such physical reinforcement results in structural hardening which prevents denting and inhibits displacement of individual optical storage devices26from the horizontal two-dimensional layout (e.g., also seeFIG. 1) when the optical storage devices are exposed to vibration (e.g., due to fan vibration, jostling from movement of the drawer30, etc.).

It should be understood that different depths of the honeycomb arrangement are suitable. For example, at least 72 2.5 inch diameter optical storage devices26easily fit within a drawer30configured for a standard 17″ rack with a drawer depth of 30″.

It should be further understood that other arrangements are suitable for use as well as such rows and columns for the devices26, triangular configurations, and so on. Such modifications and enhancements are intended to belong to various alternative embodiments of the system20. Further details will now be provided with reference toFIG. 5.

FIG. 5is a sectional view of an optical storage device26′ in accordance with a second embodiment. The optical storage device26′ is similar to the earlier-described optical storage device26, i.e., the first embodiment which is illustrated inFIG. 2. However, in contrast to the optical storage assembly26, the optical storage device26′ utilizes an optical assembly56′ which utilizes a magnetic field to control access to the various data storage locations on the storage medium54. Along these lines, the optical assembly56′ includes a magnetic field generator110having a magnet112disposed in base50and a magnetic field casing114disposed in the external space64and around the exterior of the storage medium54. The optical assembly56′ further includes a set of mirrors116(i.e., one or more mirrors116) disposed within the internal space62. The magnetic field generator110is configured to levitate and orient the set of mirrors116at a location118which is substantially central to the internal space62.

Initially, the set of mirrors116can reside in a locked down position over the magnet112. However, once the optical storage device26′ begins operation, the magnetic field generator110raises the set of mirrors116above the base50. In particular, since the casing114of the magnetic field generator110extends around the periphery of the storage medium54, the magnetic field generator110is capable of levitating and orienting the set of mirrors116in the middle of the internal space62. In this central location, the set of mirrors116is configured to adjust angular orientation in response to changes in a magnetic field and thus redirect light from a light source66′ toward targeted curved surfaces58of the storage medium54to form the holographic images98on the storage medium58(also seeFIG. 3).

In some arrangements, the set of mirrors116is configured to steer both the encoded signal beam96and the reference beam92toward the data storage locations of the storage medium54(seeFIG. 3). In these arrangements, the magnetic field generator110is configured to suspend multiple mirrors116centrally within the internal space62, and control the angular orientations of the mirrors116. In particular, magnetic field generator110steers the mirrors116in tandem so that both beams92,96accurately direct the beams92,96to the targeted storage location.

In other arrangements, the set of mirrors116is configured to steer only one of the beam96/92toward the data storage locations of the storage medium54with the other beam96/92being steered by other means. In one arrangement, a single mirror116steers the reference beam92from the director88(seeFIG. 3) to the targeted location while the SLM86steers the encoded signal beam96to the targeted location. In another arrangement, a single mirror116directs the encoded signal beam96from the SLM86to the targeted location while the director88steers the reference beam92to the targeted location.

During write operations, the reference beam92and the encoded signal beam96intersect at a particular data storage location of the storage medium54(also seeFIG. 3). At this location, the intersecting beams92/96form an interference pattern of bright and dark regions within the photosensitive recording material of the storage medium54thus generating, as a holographic image98within the storage medium54, a multi-page digital data pattern.

During read operations, light from one beam (e.g., the reference beam92reflecting off a magnetic field controlled mirror116) passes through the holographic image96. As the light passes, the globe-shaped detector array100of the light sensor68receives the light and reconstructs the data pattern.

In the configuration shown inFIG. 5, it should be understood there are minimal moving parts and thus minimal friction. Accordingly, there is little or no heat generated by the movement of the set of mirrors116. As a result, there is less demand for an air stream thus reducing costs for fans and supporting power supplies. Moreover, the lack of mechanical wear results in extended lifetimes and longer mean times between failures.

As described above, improved data storage techniques involve the use of a storage medium54having a curved surface58and an optical assembly56,56′ configured to optically write data to and read data from the curved surface58of the storage medium54. The use of such a storage medium54and optical assembly56,56′ minimizes the need for extensive travel of the optical assembly56,56′. Rather, data access operations can be effectuated by simply orienting the optical assembly56,56′ from a location which is substantially central to an internal space62defined by the curved surface58of the storage medium54. Such orientation can occur with minimal latency and travel (e.g., control of angular direction). As a result, data access times are optimized, and mechanical movement and the associated heat generation are kept to a minimum.

For example, it should be understood that the optical storage devices26(FIG. 2) were described above in the context of a high-density optical storage system20(FIG. 1) by way of example only. There are other arrangements which are suitable for use by the optical storage devices26as well. For instance, in some arrangements, the optical storage devices26are configured as stand-alone, portable storage devices. In such arrangements, a controller (e.g., see the controller38inFIG. 1) resides in the base50, and the storage medium54has a BuckyBall-like hardened exterior which enables such an optical storage device26to be placed on a desktop and connected to a laptop or desktop computer. The controller provides access to a bootable operating system, user programs, and user files. Accordingly, a user does not need to travel with a laptop. Rather, the user simply travels with the optical storage device26and connects to a processing station upon arrival. Such modifications and enhancements are intended to belong to various embodiments of the invention.