United States Patent
`Rafner
`
`119;
`
`[54]
`
`[751
`
`[73]
`
`[21]
`
`[22]
`[51]
`[52]
`
`[53]
`
`[56]
`
`MULTIPLE INDEPENDENTLY
`POSITIONABLE RECORDING-READING
`HEAD DISK SYSTEM
`
`Inventor:
`
`David J. Rafner, Golden Valley,
`Minn.
`
`Assignee:
`
`Honeywell Inc., Minneapolis, Minn.
`Appl. No.: 261,678
`Filed:
`Oct. 24, 1988
`Int. c1.s .............................................. .. G11B 7/00
`U.S. c1. ...................................... .. 369/32; 369/33;
`369/34; 369/36; 369/38; 369/178; 369/44.37;
`360/18; 360/114
`Field of Search ............. 360/22, 13, 93.01, 93.02,
`360/114, 75, 77.02, 77.03; 369/32, 34, 43-47,
`36, 35, 37, 38, 173, 13, 14, 44.37; 353/342
`References Cited
`U.S. PATENT DOCUMENTS
`3.728.699
`4/1975 Sordello ................................ 360/75
`4,371,902
`2/1983 Baxter et al.
`.
`. 360/75
`4,387,452
`6/1983 Bricot et a1.
`.
`4,422,112 12/1983
`4,577,240
`3/1986
`
`Hedberg et al.
`
`...................... 360/22
`
`[11]
`
`145]
`
`Patent Number:
`
`Date of Patent:
`
`4,972,396
`
`Nov. 20, 1990
`
`4,644,515
`4,694,358
`4,731,685
`4,371,903
`
`2/1987
`9/1987
`3/1988
`10/1989
`
`....................... 369/32
`369/14 X
`
`Allebest et al.
`Muchnik et al.
`Orcutt ........
`Carrell ............................ .. 369/44 X
`
`OTHER PUBLICATIONS
`
`“Optical Memories vie for Data Storage”, by Jeff
`Hecht, High Technology, Aug. 1987.
`
`Primary Examiner——Robert L. Richardson
`Attorney, Agent, or Firm—l-Iaugen and Nikolai
`
`ABSTRACT
`[57]
`A multiple independently positionable recording-read-
`ing head optical disk system. The system includes at
`least one optical disk having an arrangement of data
`elements. A plurality of recording-reading heads read
`and write data onto the optical disk. An apparatus for
`transporting the plurality of recording-reading heads
`over one side of the optical disk enabling each of the
`recording-reading heads to read data from or write data
`onto the optical disk independently of the other record-
`ing-reading heads.
`
`18 Claims, 3 Drawing Sheets
`
`Unified Patents Exhibit 1006, p. 1
`
`

`
`US. Patent
`
`Nov. 20, 1990
`
`‘Sheet 1 of3
`
`‘
`
`4,972,396
`
`PRIOR ART
`
`Unified Patents Exhibit 1006, p. 2
`
`

`
`US. Patent
`
`Nov. 20, 1990
`
`Sheet 2 of3
`
`4,972,396
`
`PRIOR ART
`
`PRIOR ART
`
`_f_[g. 5
`
`Unified Patents Exhibit 1006, p. 3
`
`

`
`US. Patent
`
`Nov. 20, 1990
`
`Sheet 3 of 3%
`
`4,972,396
`
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`Unified Patents Exhibit 1006, p. 4
`
`

`
`1
`
`4,972,396
`
`MULTIPLE INDEPENDENTLY POSITIONABLE
`RECORDING-READING HEAD DISK SYSTEM
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention:
`The present invention relates generally to digital disk
`storage systems and more particularly to a multiple
`independently positionable recording-reading head op-
`tical or magnetic disk system.
`II. Discussion of the Prior Art:
`FIG. 1 shows schematically a typical known single
`head optical disk positioning system. Such a system
`includes a transducing head 10 which may use focusing
`means 12 such as a laser, prism or lens. The head 10 is
`transported across an optical disk 40 typically using a
`wormscrew drive or belt drive 50 associated with a
`stepper motor 30. Because there is only one transducing
`head on such systems, there is no ability to edit, review
`or output sensor acquired data while simultaneously
`accepting an input data stream, for example.
`While some known devices use multiple transducer
`heads to access data storage disks, none of the known
`devices offer the ability of these heads to move and act
`independently of each other and either read or write
`data which was read or written by one of the other
`heads on the same side of such disks. U.S. Pat. No.
`4,644,515 to Allebest et al. discloses one example of
`such a device. Allebest et al. utilizes a substrate-based 30
`array of heads such that a disk with 54,000 tracks has
`54,000 read heads. It offers and discusses only read
`access. The device disclosed in Allebest features heads
`that are not mobile and thus carmot be used with the
`continuous track recording method wherein the tracks
`are actually a single track spiraling inward and the
`radial position of the track varies constantly. The Alleb-
`est et al. device cannot achieve truly continuous access
`to new data since a single track cannot be read by two
`heads simultaneously. Allebest et al. also faces difficul-
`ties in overcoming the technical hurdles required to be
`overcome for implementing a 54,000 head read mecha-
`nism and system support represents an order of magni-
`tude increase in prototyping and low volume produc-
`tion costs. Allebest et al. does not even address write
`capabilities for such a fixed array system.
`FIGS. 4 and 5 are schematic views of prior art disk
`systems employing single recording-reading heads. As
`shown in FIG. 4, recording reading head 60 is typically
`a magnetic transducer mounted on sweep arm 62. The
`recording-reading head then sweeps across the disk 64,
`which is typically a magnetic media type disk, through
`the control of a mechanical control means 66. Mechani-
`cal control means 66 is well known in the art and may
`be, for example, a separate motor or servo motor.
`FIG. 5 illustrates schematically another well known
`transport mechanism for a single-head system. The head
`60 is transported by cantilever arm 70 in a radial path
`traversing the disk tracks. The cantilever arm 70 is
`typically controlled by a motor 67, such as a stepper
`motor or equivalent device. As in the optical disk de-
`vice of FIG. 1, since there is only one transducing head
`on the system shown in FIGS. 4 and 5, there is no ability
`to edit, review, or output data from one area of the disk
`while simultaneously performing other equivalent tasks
`to information on other areas of the disk media.
`In contrast, the present invention discloses a multi-
`head and drive mechanism system implemented in a
`
`2
`technically feasible configuration of existing recording-
`reading heads and servo hardware.
`An excellent application of a high capacity multiple
`independently positionable
`read/write head drive
`would be on almost any advanced autonomous, semi-
`autonomous or information gathering remote vehicle or
`platform. Obvious examples include recognizance and
`deep space satellites or probes and autonomous battle-
`field robotics. In these very demanding applications, the
`flexibility of the invention to simultaneously read, write
`and alter several high bandwidth streams of data simul-
`taneously would be invaluable.
`Such applications typically have a high level of im-
`bedded signal processing and analysis capability related
`to a limitation of transmission capabilities back to their
`control center. A remotely or autonomously guided
`surveillance aircraft for example, might acquire high
`resolution, multispectral sensor and video information
`but only have the transmission capability equal to a low
`resolution video signal. If such a vehicle were equipped
`with the invention discussed herein, no significant data
`need be lost as this device would allow a heretofore
`unavailable length of time to analyze, compress, en-
`hance, prioritize or rebroadcast the data.
`In one possible situation where real time flight con-
`trol was required over a target area, the controller
`could view the low resolution image and then retroac-
`tively request specific high resolution data be sent for
`more detailed analysis. The ability of the drive to input,
`output and manipulate multiple streams of data without
`interruption means that even when transmitting se-
`lected information back to base, there need be no limita-
`tion on the continued collection and signal processing
`of new data.
`
`SUMMARY OF THE INVENTION
`
`The present invention provides a multiple indepen-
`dently positionable recording-reading head disk system
`which overcomes and alleviates the deficiencies of prior
`art systems. The disk system of the invention includes at
`least one disk having an arrangement of data elements.
`A plurality of recording-reading heads read and write
`data onto the disk. Each of the heads has a means for
`focusing onto the data. The recording-reading heads are
`transported over one side of the disk so as to enable
`each of the recording-reading heads to read and write
`data from and onto the disk independently of the other
`recording-reading heads in the system.
`It is accordingly a principal object of the present
`invention to provide a multiple independently position-
`able recording-reading head disk system wherein the
`recording-reading heads move and act independently
`and either read or write data which was read or written
`by other heads nearly simultaneously on the same side
`of an optical disk.
`Another object of the invention is to provide appara-
`tus whereby in an optical disk system editing, reviewing
`or outputting sensor acquired data may be done substan-
`tially simultaneously without interfering with an input
`data stream.
`It is yet another object of the present invention to
`provide apparatus wherein continuous and real-time
`storage of new data would not be interrupted by the
`review of any stored data on the disk.
`These and other objects and advantages of the pres-
`ent invention will become apparent to those skilled in
`the art from the following detailed description of a
`preferred embodiment, especially when considered in
`
`Unified Patents Exhibit 1006, p. 5
`
`

`
`3
`conjunction with the accompanying drawings in which
`like numerals in several views refer to corresponding
`parts.
`
`DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic view of atypical known single
`head optical disk positioning system.
`FIG. 2 is a schematic view of a dual head embodi-
`ment of the multiple independently positionable record-
`ing-reading head optical disk system of the invention.
`FIG. 3 is a schematic view of an illustrative example
`of one embodiment of the invention employing four
`optical recording-reading heads.
`FIG. 4 is a schematic illustration of a known single
`head disk system employing a recording-reading head
`mounted on a sweep arm.
`FIG. 5 is a schematic illustration of a known single
`head disk system employing a recording-reading head
`mounted in a cantilever fashion.
`FIG. 6 is a schematic view of an alternative embodi-
`ment of the invention employing a plurality of sweep-
`arm-mounted recording-reading heads.
`FIG. 7 is a schematic view of an alternative embodi-
`ment of the invention employing a plurality of cantilev-
`er-mounted recording-reading heads.
`FIG. 8 is an illustrative block diagram of a system
`application of the invention used as a very high capacity
`multiported data buffer.
`FIG. 9 is an illustrative block diagram of a system
`application of the invention as employed in a fixed qual-
`ity signal compression and transmission system.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`Referring now to FIG. 2, one embodiment of the
`present invention incorporating dual heads in a multiple
`independently positionable recording-reading head op-
`tical disk system 100 is shown schematically. While a
`dual head system is shown in FIG. 2, a nearly unlimited
`number of recording-reading heads 10 could potentially
`be utilized. However, for the purposes of explaining the
`basic concepts of the device, the dual head system
`shown in FIG. 2 will serve as an illustrative example.
`Still referring to FIG. 2, the optical disk system of the
`invention is shown including two recording-reading
`head means 10 including a means for focusing 12, opti-
`cal disk 40 having an arrangement of data elements 45
`and means for transporting the recording-reading heads
`over one side of the optical disk 40. The transporting
`means includes stepper motors 30, wormscrew drive 50,
`and extended rails 25 onto which the recording-reading
`heads 10 are mounted in a conventional fashion. It may
`be advantageous in some systems to employ a belt drive
`or equivalent known apparatus in place of wormscrew
`drive 50. The focusing means 12 may be any of several
`transducing means for reading and writing data onto an
`optical disk including a laser, prism or lens as are well
`known in the art and commercially available.
`The disk 40 has an arrangement of data elements 45
`which may be recorded in the form of minute depres-
`sions of concentric circles forming a track with a width
`less than one micrometer (typically 0.6 micrometers)
`and of a very limited depth (0.15 micrometers), the
`spacing between the tracks being less than two microm-
`eters (e.g. 1.6 micrometers) and the type of disk wherein
`the data is arranged in a series of concentric circles
`forming a track. Alternatively,
`the data may be ar-
`ranged in a continuous track forming a single track
`
`4,972,396
`
`4
`spiraling inward. In general operation, the disk 40 is
`rotated by a shaft 44. The data-carrying disk has a typi-
`cal diameter of 5—l inches. The reading and recording
`of a track in a laser-based device, for example, is per-
`formed by means of a beam from a laser source focused
`onto the disk. Other focusing means are well known in
`the art.
`Having described the basic elements of the invention,
`we now turn to some illustrative examples which are
`helpful in explaining the operation of the invention.
`Referring now to FIG. 3, an alternative embodiment
`of the invention is shown employing four recording-
`reading heads for an optical disk system. The recording-
`reading heads are mounted in a manner similar to the
`manner as described above with respect to FIG. 2.
`However, instead of the extended rails as used in FIG.
`2, the rails 27 of the embodiment shown in FIG. 3 are
`configured so as to form four radial pads for holding
`four recording-reading heads 10 and transporting those
`recording-reading heads across the top surface of the
`disk by means such as screw drive 50.
`Referring now to FIG. 6, another alternative embodi-
`ment of the invention is shown employing sweep arm
`mechanisms 62 to transport a plurality of recording-
`reading heads 60 in a sweeping motion across the top of
`a digital disk, such as a magnetic disk. As explained
`above with reference to FIG. 4, the sweep arm mecha-
`nism is well known in the art, but never before has been
`used to implement a plurality of recording-reading
`heads on a single disk as is taught by the present inven-
`tion.
`U.S. Pat. No. 4,371,902 to Baxter et al. discloses a two
`head system of the type shown in FIG. 5, however, the
`second head is specifically disclosed as a mechanism
`exclusively for reading servo positioning information
`from special tracks that are inbetween the tracks which
`store user accessible data.
`‘
`This invention, in addition to disclosing n number of
`independent head devices and positioning mechanisms,
`teaches that each of these heads is to be capable of
`reading the same tracks, upon which is stored user ac-
`cessible data. Baxter et al. does not disclose nor can it
`accomplish the novel capabilities as taught by this in-
`vention.
`Similarly, FIG. 7 shows another alternative embodi-
`ment of the invention using cantilever recording heads.
`The cantilever mechanisms are well known in the art as
`is described with respect to FIG. 5.
`In yet another illustrative example, a dual head sys-
`tem as illustrated in FIG. 2 could provide the ability to
`edit, review or output sensor acquired data without
`interfering with an input data stream. On a consumer
`level, a two-headed recording-reading optical video
`disk system would provide advantageous features over
`the current generation of magnetic tape video cassette
`recorder (VCR) equipment. For example, with the
`magnetic tape VCR technology, the viewing of a re-
`corded broadcast can only begin after the broadcast has
`been completed and the tape is rewound. With a dual
`head disk system, such as is shown in FIG. 2, however,
`regular or even accelerated viewing could begin any
`time after the recorder was activated. In a home/con-
`sumer setting, a consumer might begin recording a pro-
`gram at 7:00 pm. but begin viewing the program at 7:10
`p.m. The disk system would thus contain ten minutes of
`buffered video data. As the viewer encountered parts of
`the recorded broadcast he did not wish to watch, he
`could easily “fast forward” over the segments. In the
`
`Unified Patents Exhibit 1006, p. 6
`
`

`
`5
`above situation, independent read and write mecha-
`nisms would suflix. Dual
`recording-reading heads
`would provide the additional capability to record and-
`/or play two inputs simultaneously. Since the recording
`heads move independently and can be positioned any-
`where along the tracks of the spinning disk, one of the
`heads could be tied to the video input from the televi-
`sion, for example, while the other head outputs a de-
`layed video signal to the television screen. While the
`first head is receiving input information from the re-
`ceiver of the television, the second head would be read-
`ing tracks previously recorded by the first head ten
`minutes before.
`
`25
`
`35
`
`A three-headed system (as shown in FIG. 7) would
`provide additional features and flexibility over a simple
`dual head system. In one practical application, a T.V.
`studio or rebroadcast center equipped with a three-
`headed recording-reading optical disk system could
`continuously store network programming received by a
`satellite on an optical disk using one of the three heads.
`Using a second head, a technician could edit, enhance,
`delay, modify or delete parts of the recorded broadcast.
`One such enhancement could be the addition of cap-
`tions, image processing improvements or other modifi-
`cations of the video signal. The third head could then be
`used for output to the public, via a local broadcast or a
`cable. All three activities could be occurring simulta-
`neously with only moments of delay between the re-
`ceipt of the programming and its retransmission.
`In yet a third example, the optical disk system of the
`invention could be used in connection with a building
`security application where output from several cameras
`is normally viewed sequentially on a single monitor. A
`multi-headed optical disk system could be employed to
`provide 100 percent viewing coverage of all cameras
`while still using only a single monitor for a group of
`cameras. This could be accomplished by continuously
`buffering all inputs to the disk system and then, as the
`monitor sequentially switched to the difierent buffered
`video channels, replay the image at several times nor-
`mal speed. This feature could most easily be imple-
`mented on cameras monitoring areas in which little or
`no movement is expected. Such static scenes would not
`in any way appear distorted by high speed replay. If an
`anomaly was identified, the image could easily be re-
`played at normal speeds. With a multi-headed system,
`such as is taught by the invention, the review of any
`data, video or otherwise, would in no way interfere
`with the continuous and real-time storage of new data.
`A nearly unlimited number of heads, restricted only
`by the physical geometry of the disk mechanism, could
`potentially be utilized by the present invention. How-
`ever, for utilization scenarios requiring more than three
`concurrent iriput/output I/O channels, two or more
`separate disk systems, each with two or three heads,
`could in principle be linked with additional well known
`support electronics to accomplish nearly equivalent
`functionality.
`FIG. 8 is an illustrative block diagram of a system
`application of the invention used as a very high capacity
`multi-ported data buffer. The system of FIG. 8 com-
`prises input sources such as camera 90, receiver 92,
`and/or high band width sensors 94, which provide
`inputs to receiver and enhancement circuitry 105
`which, in turn, provides an input to a multi-head drive
`of the present invention 200. The system further com-
`prises processing apparatus 202 transmission rebroad-
`cast apparatus 204, long term output storage apparatus
`
`4,972,396
`
`6
`206 and long term input storage apparatus 208. Data
`from the drive may be transmitted for closed circuit
`viewing by apparatus 210 or output-to-output devices
`such as an earth station satellite dish 212 or, for exam-
`ple, cable TV 214. All of the above input sources, re-
`ceiver enhancement circuitry, long term storage de-
`vices,
`transmission rebroadcast circuitry and output
`devices such as the closed circuit apparatus, the earth
`station and cable TV are well known in the art. Process-
`ing of data in the form of editing, captioning enhance-
`ment analysis or compression/decompression through
`processing means 202 is also well known in the art.
`What the multi-head drive of the invention 200 allows
`the system to do is to receive data through the receiver
`enhancement circuitry 105 from one of the input
`sources and the long term storage, to send and receive
`information from the processing means 202 and then
`output processed or real time information to any or all
`of the output devices. In this manner, the multi-head
`drive 200 serves as a very high capacity multi-ported
`data buffer allowing simultaneous transmission and
`processing of data from the same disk drive.
`FIG. 9 shows another use of the multi-head drive 200
`of the invention as employed in a fixed quality signal
`compression/transmission system. As shown in the
`block diagram of FIG. 9, a full bandwidth input source
`220 supplies an input to the multi-head drive which has
`the capability of reading data into compression circuitry
`222 and receiving compressed data from compression
`circuitry 222. Such compression circuitry is well known
`in the art. The multi-head drive may then, nearly simul-
`taneously while processing input information, send out
`a fixed quality signal to output devices 212 or 214. The
`output devices, in turn, could serve as input devices to
`a second multi-head drive 200’, which would send infor-
`mation to decompression circuitry 224, which is well
`known in the art, and receive information from decom-
`pression circuitry 224 for output to a full bandwidth
`output device 226. The input source 220 and the output
`device 226 may be any full bandwidth input or output
`devices as are well known in the art.
`Today, most compression schemes for live video
`transmission allow for the degradation of the image
`when action in the image exceeds a certain threshold.
`This is because of the desire to transmit in real time and
`because there is no reasonable form of high-capacity
`buffering available. A dramatically increasing number
`of applications do not require strict real time capabili-
`ties, however.
`An excellent example of one such application would
`be a TV field crew wishing to transmit “raw feed” back
`to the production studio for incorporation into the eve-
`ning news. The cheapest method of data transmission is
`over an industry standard,
`fixed bandwidth, packet
`switching network. In this case typically a 384Kb type
`“I-I” channel. Unfortunately a video signal is usually
`composed of a random mixture of high and low activity
`shoots. A typical compression system is designed with
`an average level of activity in mind. When the activity
`is low, the compression system is not strained and trans-
`mission bandwidth goes underutilized. When the activ-
`ity level in the image is high, the compression system
`cannot accommodate all the data and it must select
`which data to allow to overflow, thus causing a degra-
`dation in the image quality. The invention discussed
`herein would provide a very large capacity buffer with
`multi-port capability and resulting in a capability to
`implement complete compression without data over-
`
`Unified Patents Exhibit 1006, p. 7
`
`

`
`20
`
`25
`
`30
`
`7
`the buffering of output into the
`flow. Furthermore,
`fixed bandwidth transmission channel would effectively
`keep the utilization of the channel at 100%.
`The invention has been described herein in consider-
`able detail in order to comply with the Patent Statutes
`and to provide those skilled in the art with the informa-
`tion needed to apply the novel principles and to con-
`struct and use such specialized components as are re-
`quired. However, it is to be understood that the inven-
`tion can be carried out by specifically different equip-
`ment and devices and that various modifications, both
`as to the equipment details and operating procedures,
`can be accomplished without departing from the scope
`of the invention itself.
`What is claimed is:
`1. A multiple independently positionable recording-
`reading head optical disk system comprising:
`a rotatable optical disk having an arrangement of data
`elements on a data reading and recording surface of
`the disk;
`a plurality of recording-reading head means for read-
`ing and writing data onto the recording surface of
`the optical disk, each of the head means having a
`means for focusing; and
`a plurality of transporting means, one associated with
`each one of the recording-reading head-means for
`moving its associated head means over one side of
`the optical disk to selectively position the associ-
`ated 3 head means relative to said recording sur-
`face, each of the transporting means being movable
`independently of the other transporting means to
`enable each of the recording-reading head means to
`be selectively positioned for performing data oper-
`ations including reading data recorded on the re-
`cording surface and writing data onto the record-
`ing surface of the optical disk, independently of the
`other recording-reading head means, and further to
`enable the recording-reading head means to per-
`form data operations simultaneously.
`2. The system of claim 1 wherein the plurality of
`reading-recording heads comprises at least two record-
`ing-reading transducer heads.
`3. The system of claim 2 wherein the transporting
`means comprises:
`(a) at least two stepper motors;
`(b) at least two extended rails wherein the rails are in
`a parallel relationship over the top of the disk; and
`(c) at least two wormscrew drives in parallel relation-
`ship to the extended rails wherein each of the
`wormscrew drives is driven by one of the stepper
`motors and acts in cooperation with the rails and_
`associated stepper motor to support and transport
`at least one of the reading-recording heads.
`4. The system as in claim 3 wherein the recording-
`reading heads comprise laser recording-reading trans-
`ducer heads.
`'
`5. The system of claim 3 wherein the focusing means
`comprises a lens.
`6. The system of claim 3 wherein the focusing means
`comprises a prism.
`
`4,972,396
`
`8
`7. The system of claim 1 wherein the plurality of
`recording-reading head means comprise laser record-
`ing-reading transducer heads.
`8. The system of claim 1 wherein the focusing means
`comprises a lens.
`9. The system of claim 1 wherein the focusing means
`comprises a prism.
`10. A multiple independently positionable recording-
`reading head optical disk system comprising:
`a rotatable optical disk having an arrangement of data
`elements on a data reading and recording surface of
`the disk;
`two recording-reading transducer heads for perform-
`ing data operations including reading data re-
`corded on the recording surface and writing data
`onto the recording surface each having a means for
`focusing;
`at least two stepper motors;
`at least two extended rails wherein the rails are in a
`parallel relationship across the disk and extend
`beyond the circumference of the disk; and
`at least two wormscrew drives in parallel relationship
`to the extended rails wherein each of the worm-
`screw drives is driven by one of the stepper motors
`and acts in cooperation with the adjacent rail and
`associated stepper motor to support and transport
`one of the recording-reading transducer heads,
`each of the stepper motors operable independently
`of the other to selectively position its associated
`recording-reading head for performing data opera-
`tions independently of and simultaneously with any
`other ones of said reading-recording transducer
`heads.
`11. The system of claim 10 wherein the focusing
`means is a laser.
`12. The system of claim 10 wherein the focusing
`means is a lens.
`‘
`13. The system of claim 10 wherein the focusing
`means is a prism.
`14. The system of claim 10 wherein the optical disk
`data element arrangement is a single spiral.
`15. The system of claim 10 wherein the optical disk
`data element arrangement comprises a plurality of con-
`centric circular tracks.
`16. The system of claim 1 wherein the optical disk
`data element arrangement comprises a spiral track.
`17. The system of claim 1 wherein the optical disk
`data element arrangement comprises a plurality of con-
`centric circular tracks.
`18. A multiple independently positionable recording-
`reading head disk system comprising:
`a rotatable disk having an arrangement of data ele-
`ments on a data reading and recording surface of
`the disk;
`a plurality of recording-reading head means for read-
`ing and writing data onto the disk; and
`means for transporting the plurality of recording-
`reading head means over one side of the disk so as
`to enable each of the recording-reading head means
`to read data from or write data onto the disk inde-
`pendently of the other recording-reading heads.
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`Unified Patents Exhibit 1006, p. 8