CA1115838A - Information storage and retrieval system - Google Patents
Information storage and retrieval systemInfo
- Publication number
- CA1115838A CA1115838A CA299,591A CA299591A CA1115838A CA 1115838 A CA1115838 A CA 1115838A CA 299591 A CA299591 A CA 299591A CA 1115838 A CA1115838 A CA 1115838A
- Authority
- CA
- Canada
- Prior art keywords
- light beam
- modulated light
- film
- deformable film
- recited
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B17/00—Guiding record carriers not specifically of filamentary or web form, or of supports therefor
- G11B17/32—Maintaining desired spacing between record carrier and head, e.g. by fluid-dynamic spacing
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
- G11B19/20—Driving; Starting; Stopping; Control thereof
- G11B19/24—Arrangements for providing constant relative speed between record carrier and head
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
- G11B27/36—Monitoring, i.e. supervising the progress of recording or reproducing
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/002—Recording, reproducing or erasing systems characterised by the shape or form of the carrier
- G11B7/0037—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with discs
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/095—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble
- G11B7/0953—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for eccentricity of the disc or disc tracks
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B9/00—Recording or reproducing using a method not covered by one of the main groups G11B3/00 - G11B7/00; Record carriers therefor
- G11B9/04—Recording or reproducing using a method not covered by one of the main groups G11B3/00 - G11B7/00; Record carriers therefor using record carriers having variable electric resistance; Record carriers therefor
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/21—Intermediate information storage
- H04N1/2166—Intermediate information storage for mass storage, e.g. in document filing systems
- H04N1/217—Interfaces allowing access to a single user
- H04N1/2175—Interfaces allowing access to a single user with local image input
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/76—Television signal recording
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Optical Recording Or Reproduction (AREA)
- Optical Record Carriers And Manufacture Thereof (AREA)
Abstract
ABSTRACT
Information is stored, using a relatively low-power light beam, by redistributing the material in a deformable film. In a disc configuration, positioning of the light beam is achieved by referencing to a previously re-corded track. In a document storage and retrieval system the document is scanned with the resultant scanned signal modulating the writing light beam producing a recorded track. This track is optically read with the resultant signal applied to a printer. For optimum utilization of the area, the re-cording and readout take place at constant velocity.
Information is stored, using a relatively low-power light beam, by redistributing the material in a deformable film. In a disc configuration, positioning of the light beam is achieved by referencing to a previously re-corded track. In a document storage and retrieval system the document is scanned with the resultant scanned signal modulating the writing light beam producing a recorded track. This track is optically read with the resultant signal applied to a printer. For optimum utilization of the area, the re-cording and readout take place at constant velocity.
Description
~il5838 BACKGROUND OE THE INVENTION
1. Field of the Invention This invention relates to document storage and retrieval systems.
In a primary application the invention relates to storing information by using a modulated light source to redistribute the material of a deformable film coating.
1. Field of the Invention This invention relates to document storage and retrieval systems.
In a primary application the invention relates to storing information by using a modulated light source to redistribute the material of a deformable film coating.
2. Description of Pr:lor Art A variety of file systems have been considered for storing many documents onto a high resolution material. Microfilm systems optically re-duce the original and photograph it on a high resolution emulsion. Photo-graphic systems of this type, including scanned photographic systems, require time-consuming wet photography.
1~15838 Thus new entries to the file take considerable time to be made available. In addition portions of a photographic film storage medium cannot be separately addressed at different times because the development process normally encom-passes the entire film. Thus new documents cannot be added to an existing photographic storage medium. Photographic storage appears best-suited to ap-plications where the entire plate is exposed in a single interval such as United States Patent 3,198,880 Photographic Disc Reproduction System for Tel-evision Signals" issued to P.M.G. Toulon on August 3, 1965.
One solution to the problem of having the stored information immed-iately available is described in United States Patent 3,314,073 "Laser Re-corder with Vaporizable Film" issued to Carl H. Becker on October 20, 1964.
In this system a thin thermally vaporizable film is coated onto a plastic sub-strate. An intense laser, focused on the coating, is used to vaporize the coating and produce arrays of transparent holes representing the information being stored. These can be immediately read out using light sources imaged at the holes.
This system, however, has a number of practical problems. Firstly, the large energies required to vaporize the film can only be realized by very expensive, high power lasers at the desired writing speeds. Secondly the strip format of the recording material, in the form of motion picture film, results in relatively slow accessing times to specific regions. Also the lack of an accurate tracking method results in relatively low resolution and thus inefficient use of the area in recording data.
Rapid accessing times can be achieved using the disc format where the radial motion is used to find the desired document and the circumferential motion is used to rapidly read it out. Disc recording is normally used in ap-plications where the entire disc is written on a single sequence. For example in the recording of television programs, as is done in the MCA Disco-Vision system, the entire disc is written at one time and copies are made from it.
In document storage systems, however, where individual documents are added at different times, the disc presents serious tracking problems. If the disc is removed and then remounted, the resultant ~115838 eccentricities of the tracks from a slightly off-center mounting can cause the tracks to cross and thus be destroyed. If large guard spaces are used to avoid track crossing, the storage area is used inefficiently and a limited number of documents can be stored. In addition to eccentricities, various warping and distortions of the recording media can also cause the subsequently recorded tracks to cross with previously recorded tracks and thus destroy the stored information.
In the MCA Disco-Vision system, as with other disc recording sys-tems, the information is recorded and played back at constant angular veloc-ity. This makes inefficient use of the area of the disc and results in re-cording power problems. Much greater recording power is needed in the outer diameter parts of the disc because of the increased relative motion between the disc and the modulated recording light source. In addition, the inner di-ameters have resolution problems because the information is packed more close-ly together. A given data rate, at the reduced relative motion, results in greater packing density. A relatively large inner region of the disc is often unused because of this consideration.
SUMMARY OF THE INVENTION
An object of this invention is to provide an information storage system which allows rapid writing from relatively low-power sources in a for-mat which can be immediately read.
It is also an object of this invention to provide a document storage and retrieval system where the documents are rapidly scanned, stored on a rel-atively ~nexpensive media using a low power source, and are capable of being immediately and rapidly accessed, read out and printed.
It is a further object of this invention to provide a method of high-density recording on a disc without the recorded tracks overlapping due to distortion of the disc or a lack of concentricity during each recording interval.
It is a further object of this invention to provide a method of ef-ficiently utilizing the area of the disc and the recording power by recording at a constant linear velocity.
Briefly, in accordance with the invention, a recording medium is used consisting - 3a -ill583~
of a deformable film deposited on a disc-shaped substrate. A
modulated liqht beam causes local redistributions of the material of the deformable film resulting in information storage. To insure that the recorded tracks do not overlap, yet have a high packing density, a tracking light beam is used, having a fixed radial distance with respect to the modulated light beam, so that the tracks are accurately recorded with respect to the previously recorded track. For optimum use of the area of the disc, and to provide constant recording power requirements, the disc is rotated so as to maintain a constant linear velocity of the modulated light beam with respect to the rotating disc.
In a document storage and retrieval system the document is scanned with the resultant signal modulating the writing light beam. On readout, the readout light beam produces a recording signal which is applied to a printer.
According to one broad aspect of the present invention, there is provided an apparatus for recording information as variations in reflectance comprising: a metallic deformable film deposited on a substrate in a disc format; a modulated light beam representing the information to be recorded focused onto the metallic deformable film having an intensity which is sufficient to liquefy but not vaporize the material of the metallic deformable film resulting in a redistribution of the material of the metallic deformable film which changes the reflectance of a readout light beam; and means for rotating the disc with respect to the modulated light beam and radially translating the modulated light beam to produce a pattern of recorded reflectivity information.
According to another broad aspect of the present invention, there is provided a method for recording information as variations in reflectance the steps of: modulating a light ; 4 ~115838 beam with the information to be recorded; focusing the modulated light beam on a metallic deformable film deposited on a rotating disc; radially translating the modulated light beam with respect to the disc; and redistributing the material of the metallic deformable film in the region of the focused modulated light beam to change its reflectance with the modulated light beam having sufficient energy to liquefy but not vaporize the material.
For a more complete disclosure of the invention, reference can be made to the following detailed description of several illustrative embodiments thereof which is given in con-junction with the accompanying drawings, of which:
Figure 1 is a schematic representation of an embodiment of the invention using a rotating disc;
Figure 2 is a cross-sectional representation of an embodiment of the storage medium;
Figure 3 is a schematic representation of a tracking system; and Figure 4 is a schematic representation of an embodi-ment of the storage medium using electrical energy for addressing.
It is often desired to store information from documents and subsequently read them out in an automatic fashion to replace manual files. A convenient method of storage is the disc configuration shown in Figure 1 where the data from the documents become tracks on the disc such as track 27 on disc 10.
The original document, not shown, is scanned on document scanner 14. This can be a conventional facsimile scanner having the document on a rotating drum or a flatbed structure. The resultant , 4a . ;
~5838 scanned signal, in an appropriate form, is used to modulate the light from laser 12. This appropriate form can be the analog signal itself, or pref-erably a frequency modulated form of the signal where different values of reflectance on the document represent different frequencies in the signal.
Alternatively, the scanned signal can be a digital representation of the doc-ument information. In this form it is convenient to use various forms of bandwidth compression, if desired.
The scanned signal is applied to modulator 13 which modulates the light from laser 12. The resultant modulated light beam 28, in reasonably collimated fashion is directed so as to be focused on the surface of disc 10.
It goes through partially silvered mirror 22, is reflected by mirror 23, and goes through linear actuator 20 and pickup arm 26 to the recording region.
Linear actuator 20 is used to move the pickup arm 26 radially with respect to rotating disc 10 while allowing the modulated light beam 28 to pass through. The modulated light beam is reflected by mirror 24 onto air bear-ing assembly 25 which includes the objective lens. The air bearing maintains the objective lens at a fixed distance from the surface of disc 10 to insure that the beam will be focused and produce a diffraction-limited spot.
Previous recording systems have used photographic emulsions. Al-though these are very sensitive, having modest light requirements, they re-sult in a very limited and inconvenient system. The stored document infor-mation cannot be immediately read out since an awkward photographic develop-ment operation is required. Systems such as United States Patent 3,314,073 described in the description of prior art, have used a vaporizable film where the laser power renders the film into the gaseous state and removes the material. These systems require very high laser powers and are thus awkward, expensive, and have limited data writing rates. In the system described here, a novel approach is used where the laser power causes a local deforma-tion on a film by redistributing the material. Significantly reduced power is required since the material is not brought to the gaseous state. Also, ~lS838 since these redistributions are of a form which can be optically read out, the stored infor~ation is immediately available without any further proces-sing. The size of the redistribution regions can be carefully controlled, using this reduced power, so as to provide high storage density.
Disc 10 consists of coating 31 on substrate 30. The coating can be a thin metallic film such as a 400 Angstrom film of tellurium. Coatings in the thickness range from 100 to 500 Angstroms would appear to be suit-able. The material should be such that, with modest energies, it is brought momentarily to the liquid state. In this state, through surface tension, the material redistributes itself in a manner which allows it to be subse-quently read out.
The same configuration of Figure 1 can be used for reading out the stored document and displaying it. Light beam 28 from laser 12 is now used in an unmodulated fashion with document scanner 14 and modulator 13 not functioning. This light beam, focused on recorded track 27 is selectively reflected by the redistributions of material on deformable film 31 to create a reflected light beam containing the document information. This light beam traverses the same path as the incident light beam, in the opposite direc-tion. Part of it is reflected by partially silvered mirror 22 and detected by detector 15. This detector can be a photocell which produces the record-ing signal 29. This signal can be applied to printer 16 which is a standard facsimile printer using any of a variety of techniques to convert signal 29 into variations of reflectance on a substrate. Some of the printing methods currently used include electrochemical, thermal, electrostatic, and mechan-ical. These are all commercially available. Alternatively, the signal can be applied to a television type display system where it can be viewed. An intermediate storage system can be used to store the recording signal so that it can be repeatedly applied to the display.
Previous disc recording systems have used constant angular veloc-ity, with the motor speed remaining cDnstant. This results in increased 1~1583t~
writing power requirements at the outer radii of the disc where the linearvelocity is greatest. In addition, the area of the disc is inefficiently used since the data is excessively packed together at the inner radii.
Usually only a limited area of the disc is used in these systems. In Fig-ure 2, these problems are solved by recording and playing back with a cons-tant linear velocity.
On recording a radial indicating signal 21 is derived from linear actuator 20 which indicates the radial position of the objective lens assem-bly 25. This radial indicating signal is applied to motor speed control 19 which controls motor ll such that the product of the radiusand the motor speed remain a constant. This provides constant linear velocity of the foc-used modulated light beam with respect to the surface of the disc 10.
On playback, recording signal 29 is applied to the data rate mon-itor 17. This monitor measures the data rate of this signal 29 and applies an error signal 18 to motor speed control 19 so as to keep the data rate constant. A constant data rate corresponds to constant linear velocity if the track has been recorded at constant linear velocity.
The data rate monitor can simply measure the bit rate if a digital format is used. If a frequency modulated format is used the data rate mon-i.tor can measure the frequency during the synchronization pulse regionswhere the frequency should be a constant. Alternatively, if a buffered sys-tem is used with the printer 16, the data rate monitor can measure the status of the buffer.
Figure l shows an embodiment where the recording and playback are conveniently used in a single system. In some applications it may be more convenient to use separate systems. For example, a disc containing a number of stored documents could be used with a number of readout systems where these documents are printed out or displayed. The readout-only system nor-mally requires a lower power light source and no light modulator and is thus less expensive.
~115838 In many existing systems all of the information is written onto the disc at a single time interval without ever removing the disc and re-placing it. In these the registration of each newly written track with re-spect to the previously recorded tracks is reasonably accurate since there is no problem of concentricity. However, even in these systems, subtle warpage or other distortions of the disc between recording periods can cause problems. The newly recorded tracks can overlap previously recorded tracks, thus destroying information. This problem is avoided by increasing track spacing, thus reducing the storage capability.
This tracking problem is particularly aggravated in systems where the disc is removed and then replaced, as would be the case in the desirable versatile arrangements. Here the eccentricity caused by the replaced disc not being exactly centered again can cause the tracks to cross and destroy information. If guard bands are placed between recording intervals, much of the information storage capacity is lost.
This problem is solved by the unique approach illustrated in Fig-ure 2. Here the focused modulated light beam 42 is referenced to a prev-iously recorded track 41 so as to insure that the tracks maintain the de-sired spacing independent of eccentricity or distortion. Initially a refer-ence track is written on the outer periphery of the disc. This can be doneusing a lead screw to radially drive a light source while the disc is being rotated. A tracking light source, positioned a fixed radial distance with respect to the modulated light source, is used to track the reference track and thus position the writing beam. As new tracks are written, the tracking beam tracks those to accurately position the focused modulated light beam with respect to the previously recorded track.
In Figure 2 the modulated light beam 28 is produced by an argon laser source 12 and modulator 13. This beam is transmitted through di-chroic mirrors 51 and 43. These mirrors are transmissive to the shorter wavelength of the argon laser and reflective or partially reflective to the .f . ~
illS838 longer wavelength of the helium neQn laser 46 which is the source of the tracking light beam 52. The modulated light bea~ 28 is then reflected off controllable mirror 24 and focused by objective lens 40 onto the surface of rotating disc 10 to produce focused modulated light beam 42.
The tracking light beam 52 is reflected from dichroic mirror 51 and is partially transmitted by the partially reflective dichroic mirror 43. It is then also reflected off controllable mirror 24, at a slightly different angle, and focused by lens 40 to produce a focused tracking beam at track 41 which is displaced a fixed radial distance from the focused mod-ulated light beam 42. The light reflected from track 41 traverses the same optical path in the opposite direction and is partially reflected off par-tially reflecting dichroic mirror 43. This reflected beam is focused by lens 50 onto adjacent photocells 48 and 49. Their outputs are applied to difference amplifier 47. This amplifier subtracts the two photocell outputs to form error signal 53. This signal will be zero when the two outputs are equal which corresponds to the focused tracking beam being exactly on the previously recorded track 41. If it is off on either side, either photocell 48 or 49 will have a greater output, generating a positive or negative error signal 53. This error signal is coupled to the mirror actuator system 45 which drives rotator 44 and thus pivots mirror 24 in response to signal 53.
The mirror actuator system 45 can be a servo-amplifier with rotator 44 a servo-motor. As mirror 24 rotates the focused tracking light beam is brought onto the center of previously recorded track 41 and the focused modulated light beam 42 is simultaneously moved to remain a fixed radial distance from the focused tracking light beam. Thus the focused modulated light beam is kept a fixed radial distance from the previously recorded track.
The mirror 24, rotator 44 and objective lens holder 25 are all supported by pickup arm 26 of Figure 1. This pickup arm is moved radially by linear actuator 20 which provides the coarse radial motions which brings the tracking system into the vicinity of the correct track. The rotating lliS838 tracking mirror 24 has a range of a number of tracks so that the coarse radial position provided by linear actuator 20 needn't be very accurate.
The tracking light system can also be used in the readout mode without using the modulated light beam 28 from the argon laser 12. As the focused tracking light beam tracks the previously recorded tracks it is providing a readout of these tracks in addition to a tracking error signal 53. For example the output of either photocell, such as 48 as shown, can be used for the recording signal 29 which is then applied to the display system or printer 16. Alternatively, the sum of the two photocells 48 and 10 49 can be used for recording signal 29.
Assembly 25 in Figures 1 and 2 contains the objective lens 40 which must be kept a fixed distance from the surface of disc 10. This can be accomplished by an air bearing system such as the one desc~ibed in United States Patent 3,947,888 "Hydrodynamic Bearing Head Providing Constant Spac-ing" issued to Manfred H. Jarsen On March 30, 1976.
As shown in Figure 3, a number of methods may be used to redis-tribute the material in deformable film 31. Referring to the upper layers only and ignoring the lower layers, the incident energy causes the material in film 31 to become momentarily liquified. Due to phenomena such as sur-20 face tension the material redistributes itself in a new configuration whichcan be subsequently read out. With sufficient incident power the material in deformable film 31 will redistribute itself so as to form a void 33.
This can be read out in a number of ways. For example, the variation in light transmission can be measured by transmitting a focused readout beam through the film to a photocell on the other side of the substrate. Gen-erally, however, it is more convenient to have the readout beam measure var-iations in reflected light as shown in Figures 1 and 2.
The variations in reflection can be enhanced by the use of an ad-ditional antireflection coating 32 placed between the deformable film 31 and 30 the light source. Firstly, however, this film has an important function in 11~5838 the writing operation by matching the modulated light beam to the deform-able film 31. Anti-reflection coating 32 can provide matching by being a quarter wave thick at the writing wavelength and having a refractive index which is the geometric mean of that of free space and that of the deform-able film. Alternatively it can be a more complex multilayer coating. The film will thus minimize the reflections of the modulated light beam so that most of the energy goes into deformable film 31.
The coating 31 can serve a variety of functions in the reflective readout mode. For example it can minimize the reflections of the readout beam from the film, and result in large reflections in the vicinity of voids 33 because the coating 32 is intentionally not matched to the sub-strate material 30. Alternatively, when using a readout wavelength differ-ent from that of the writing beam, a relatively large reflection can be ob-tained at the metal film and a small reflection at the void since, at the readout wavelength, the coating 32 is better matched to the substrate 30 than the deformable film 31. Here the readout signal will have the opposite polarity since it will decrease in the written regions.
The power requirements are further diminished by having the modu-lated light beam liquefy only the upper portion of the film. Here the ma-terial will redistribute itself in the forms shown in 34 and 35. In 34 the material has redistributed itself into a concave region and in 35 it has become a concave diffuse region because of the material used. These are ~lso read out due to their varying reflectivity. This variation is due to combinations of effects. One effect is the partial destruction of the matching between anti-reflection coating 32 and the deformable film 31 due to the small separation. This causes increased reflections at the exposed regions. Another effect is the spreading of the reflected light caused by the concavity 34. This can cause an effective increase or decrease in re-flectivity depending on the remainder of the optical system. The lens action of the concavity can cause the reflected beam to be more or less lilS~38 concentrated on the receiving photocell as determined by the optics. The diffuse region 35 will, in general, cause a spreading of the light beam without lens action. This effect alone will result in an effective decrease in reflectivity.
It is important to note that the particular mode of operation is determined by the power level of the modulated light beam. To maintain this at its proper value, the newly written track can be immediately read out with the resultant signal used to control the power of the modulated light beam. The readout should be done at some information independent portion of the track, such as a portion corresponding to a synchronization region, which should always produce the same readout signal.
The ability to use the anti-reflection coating 32, with its many advantages is a result of the novel recording scheme used where the film ma-terial is redistributed by the modulated light beam. In the prior art, where high powers are used to vaporize the material, this coating could not be used since it does not permit the escape of the vaporized material.
As shown in Pigure 3, both sides of the disc can be used. An ad-ditional deformable film 31 and anti-reflection coating 32 is deposited on the underside of the substrate 30. This can be separately written on and read out in the same manner previously described to double the storage cap-acity of each disc.
In the systems discussed thusfar the writing modulated light beam itself caused the redistribution of material in the deformable film 31. An alternate embodiment is shown in Figure 4 where the modulated light beam acts as a control of another energy source which contributes to the process of redistributing the material in deformable film 31. Here a photoconductor 60 and a transparent conductor 61 are deposited on the deformable film 31.
If desired, these coatings can also have some of the anti-reflection proper-ties of coating 32 previously described. In addition, substrate 30 is made of conductive material. A power source 62 is connected between the trans-parent conductor ~1 and the conducting substrate 30. The modulated light beam 28, as before, is focused by objective lens 40 to form a focused spot 42 in the region of the photoconductive coating 60 and the deformable film 31. This focused modulated light beam changes the photoconductor from an insulator to a conductor, thus completing the electrical path in the vicin-ity of the focused light beam 42. This electrical energy is then applied to that region of deformable film 31 and contributes to the process of re-distributing the material of the film to create the writing action.
Although most of the embodiments illustrated used readout in the reflection mode, light transmission can also be used where the readout beam and photocell pickup are on opposite sides of the disc. This mode, how-ever, is limited to the redistribution arrangement 33 of Figure 3 where a void is created. It is also limited to recording the information on one side of the substrate 30.
Formats other than the disc format illustrated can be used with this system. The deformable film can be used in a rotating drum configura-tion with the light sources appropriately translated along the axis of the drum. Alternatively the deformable film can be used in a flat bed format where the light beams are mechanical or electro-optically scanned across the stationary deformable film. In all of the formats the tracking while writing can be accomplished by referencing to a previously recorded track as was de-scribed for the disc format.
The systems as described used the signal from a scanned document to modulate the writing light beam to produce the redistributions of mate-rail on the deformable film. The information used to modulate the light beam can, of course, be any signal source. One important application is the storage of digital information. Thus modulator 13 in Figure 1 can be driven by a digital signal derived from a computer. The signal 29 read out by de-tector 15 will then be the desired digital information.
The track format on disc 10 will generally be a spiral so that continuous information can be recorded over more than one track. In some applications, however, it may be convenient to use a concentric ring format.
In this case the linear actuator 20, rather than moving continuously, moves in radial steps following each revolution of disc 10.
Under some conditions disc 10 in Figures 1 and 2 may be subject to excessive vibration. Under those circumstances air bearing assembly 25 may not be able to adequately follow these variations, especially when they occur at a relatively high frequency. This problem is solved by the use of a forced air system, not shown, on the underside of the disc 10. This forced air can be derived from an annular array of apertures positioned under the disc. The air creates a force proportional to position which both reduces the amplitude and frequency of the vibration. In addition, it provides a viscous force which damps the vibration. These effects bring the variations within the range of air bearing assembly 25.
~ 7
1~15838 Thus new entries to the file take considerable time to be made available. In addition portions of a photographic film storage medium cannot be separately addressed at different times because the development process normally encom-passes the entire film. Thus new documents cannot be added to an existing photographic storage medium. Photographic storage appears best-suited to ap-plications where the entire plate is exposed in a single interval such as United States Patent 3,198,880 Photographic Disc Reproduction System for Tel-evision Signals" issued to P.M.G. Toulon on August 3, 1965.
One solution to the problem of having the stored information immed-iately available is described in United States Patent 3,314,073 "Laser Re-corder with Vaporizable Film" issued to Carl H. Becker on October 20, 1964.
In this system a thin thermally vaporizable film is coated onto a plastic sub-strate. An intense laser, focused on the coating, is used to vaporize the coating and produce arrays of transparent holes representing the information being stored. These can be immediately read out using light sources imaged at the holes.
This system, however, has a number of practical problems. Firstly, the large energies required to vaporize the film can only be realized by very expensive, high power lasers at the desired writing speeds. Secondly the strip format of the recording material, in the form of motion picture film, results in relatively slow accessing times to specific regions. Also the lack of an accurate tracking method results in relatively low resolution and thus inefficient use of the area in recording data.
Rapid accessing times can be achieved using the disc format where the radial motion is used to find the desired document and the circumferential motion is used to rapidly read it out. Disc recording is normally used in ap-plications where the entire disc is written on a single sequence. For example in the recording of television programs, as is done in the MCA Disco-Vision system, the entire disc is written at one time and copies are made from it.
In document storage systems, however, where individual documents are added at different times, the disc presents serious tracking problems. If the disc is removed and then remounted, the resultant ~115838 eccentricities of the tracks from a slightly off-center mounting can cause the tracks to cross and thus be destroyed. If large guard spaces are used to avoid track crossing, the storage area is used inefficiently and a limited number of documents can be stored. In addition to eccentricities, various warping and distortions of the recording media can also cause the subsequently recorded tracks to cross with previously recorded tracks and thus destroy the stored information.
In the MCA Disco-Vision system, as with other disc recording sys-tems, the information is recorded and played back at constant angular veloc-ity. This makes inefficient use of the area of the disc and results in re-cording power problems. Much greater recording power is needed in the outer diameter parts of the disc because of the increased relative motion between the disc and the modulated recording light source. In addition, the inner di-ameters have resolution problems because the information is packed more close-ly together. A given data rate, at the reduced relative motion, results in greater packing density. A relatively large inner region of the disc is often unused because of this consideration.
SUMMARY OF THE INVENTION
An object of this invention is to provide an information storage system which allows rapid writing from relatively low-power sources in a for-mat which can be immediately read.
It is also an object of this invention to provide a document storage and retrieval system where the documents are rapidly scanned, stored on a rel-atively ~nexpensive media using a low power source, and are capable of being immediately and rapidly accessed, read out and printed.
It is a further object of this invention to provide a method of high-density recording on a disc without the recorded tracks overlapping due to distortion of the disc or a lack of concentricity during each recording interval.
It is a further object of this invention to provide a method of ef-ficiently utilizing the area of the disc and the recording power by recording at a constant linear velocity.
Briefly, in accordance with the invention, a recording medium is used consisting - 3a -ill583~
of a deformable film deposited on a disc-shaped substrate. A
modulated liqht beam causes local redistributions of the material of the deformable film resulting in information storage. To insure that the recorded tracks do not overlap, yet have a high packing density, a tracking light beam is used, having a fixed radial distance with respect to the modulated light beam, so that the tracks are accurately recorded with respect to the previously recorded track. For optimum use of the area of the disc, and to provide constant recording power requirements, the disc is rotated so as to maintain a constant linear velocity of the modulated light beam with respect to the rotating disc.
In a document storage and retrieval system the document is scanned with the resultant signal modulating the writing light beam. On readout, the readout light beam produces a recording signal which is applied to a printer.
According to one broad aspect of the present invention, there is provided an apparatus for recording information as variations in reflectance comprising: a metallic deformable film deposited on a substrate in a disc format; a modulated light beam representing the information to be recorded focused onto the metallic deformable film having an intensity which is sufficient to liquefy but not vaporize the material of the metallic deformable film resulting in a redistribution of the material of the metallic deformable film which changes the reflectance of a readout light beam; and means for rotating the disc with respect to the modulated light beam and radially translating the modulated light beam to produce a pattern of recorded reflectivity information.
According to another broad aspect of the present invention, there is provided a method for recording information as variations in reflectance the steps of: modulating a light ; 4 ~115838 beam with the information to be recorded; focusing the modulated light beam on a metallic deformable film deposited on a rotating disc; radially translating the modulated light beam with respect to the disc; and redistributing the material of the metallic deformable film in the region of the focused modulated light beam to change its reflectance with the modulated light beam having sufficient energy to liquefy but not vaporize the material.
For a more complete disclosure of the invention, reference can be made to the following detailed description of several illustrative embodiments thereof which is given in con-junction with the accompanying drawings, of which:
Figure 1 is a schematic representation of an embodiment of the invention using a rotating disc;
Figure 2 is a cross-sectional representation of an embodiment of the storage medium;
Figure 3 is a schematic representation of a tracking system; and Figure 4 is a schematic representation of an embodi-ment of the storage medium using electrical energy for addressing.
It is often desired to store information from documents and subsequently read them out in an automatic fashion to replace manual files. A convenient method of storage is the disc configuration shown in Figure 1 where the data from the documents become tracks on the disc such as track 27 on disc 10.
The original document, not shown, is scanned on document scanner 14. This can be a conventional facsimile scanner having the document on a rotating drum or a flatbed structure. The resultant , 4a . ;
~5838 scanned signal, in an appropriate form, is used to modulate the light from laser 12. This appropriate form can be the analog signal itself, or pref-erably a frequency modulated form of the signal where different values of reflectance on the document represent different frequencies in the signal.
Alternatively, the scanned signal can be a digital representation of the doc-ument information. In this form it is convenient to use various forms of bandwidth compression, if desired.
The scanned signal is applied to modulator 13 which modulates the light from laser 12. The resultant modulated light beam 28, in reasonably collimated fashion is directed so as to be focused on the surface of disc 10.
It goes through partially silvered mirror 22, is reflected by mirror 23, and goes through linear actuator 20 and pickup arm 26 to the recording region.
Linear actuator 20 is used to move the pickup arm 26 radially with respect to rotating disc 10 while allowing the modulated light beam 28 to pass through. The modulated light beam is reflected by mirror 24 onto air bear-ing assembly 25 which includes the objective lens. The air bearing maintains the objective lens at a fixed distance from the surface of disc 10 to insure that the beam will be focused and produce a diffraction-limited spot.
Previous recording systems have used photographic emulsions. Al-though these are very sensitive, having modest light requirements, they re-sult in a very limited and inconvenient system. The stored document infor-mation cannot be immediately read out since an awkward photographic develop-ment operation is required. Systems such as United States Patent 3,314,073 described in the description of prior art, have used a vaporizable film where the laser power renders the film into the gaseous state and removes the material. These systems require very high laser powers and are thus awkward, expensive, and have limited data writing rates. In the system described here, a novel approach is used where the laser power causes a local deforma-tion on a film by redistributing the material. Significantly reduced power is required since the material is not brought to the gaseous state. Also, ~lS838 since these redistributions are of a form which can be optically read out, the stored infor~ation is immediately available without any further proces-sing. The size of the redistribution regions can be carefully controlled, using this reduced power, so as to provide high storage density.
Disc 10 consists of coating 31 on substrate 30. The coating can be a thin metallic film such as a 400 Angstrom film of tellurium. Coatings in the thickness range from 100 to 500 Angstroms would appear to be suit-able. The material should be such that, with modest energies, it is brought momentarily to the liquid state. In this state, through surface tension, the material redistributes itself in a manner which allows it to be subse-quently read out.
The same configuration of Figure 1 can be used for reading out the stored document and displaying it. Light beam 28 from laser 12 is now used in an unmodulated fashion with document scanner 14 and modulator 13 not functioning. This light beam, focused on recorded track 27 is selectively reflected by the redistributions of material on deformable film 31 to create a reflected light beam containing the document information. This light beam traverses the same path as the incident light beam, in the opposite direc-tion. Part of it is reflected by partially silvered mirror 22 and detected by detector 15. This detector can be a photocell which produces the record-ing signal 29. This signal can be applied to printer 16 which is a standard facsimile printer using any of a variety of techniques to convert signal 29 into variations of reflectance on a substrate. Some of the printing methods currently used include electrochemical, thermal, electrostatic, and mechan-ical. These are all commercially available. Alternatively, the signal can be applied to a television type display system where it can be viewed. An intermediate storage system can be used to store the recording signal so that it can be repeatedly applied to the display.
Previous disc recording systems have used constant angular veloc-ity, with the motor speed remaining cDnstant. This results in increased 1~1583t~
writing power requirements at the outer radii of the disc where the linearvelocity is greatest. In addition, the area of the disc is inefficiently used since the data is excessively packed together at the inner radii.
Usually only a limited area of the disc is used in these systems. In Fig-ure 2, these problems are solved by recording and playing back with a cons-tant linear velocity.
On recording a radial indicating signal 21 is derived from linear actuator 20 which indicates the radial position of the objective lens assem-bly 25. This radial indicating signal is applied to motor speed control 19 which controls motor ll such that the product of the radiusand the motor speed remain a constant. This provides constant linear velocity of the foc-used modulated light beam with respect to the surface of the disc 10.
On playback, recording signal 29 is applied to the data rate mon-itor 17. This monitor measures the data rate of this signal 29 and applies an error signal 18 to motor speed control 19 so as to keep the data rate constant. A constant data rate corresponds to constant linear velocity if the track has been recorded at constant linear velocity.
The data rate monitor can simply measure the bit rate if a digital format is used. If a frequency modulated format is used the data rate mon-i.tor can measure the frequency during the synchronization pulse regionswhere the frequency should be a constant. Alternatively, if a buffered sys-tem is used with the printer 16, the data rate monitor can measure the status of the buffer.
Figure l shows an embodiment where the recording and playback are conveniently used in a single system. In some applications it may be more convenient to use separate systems. For example, a disc containing a number of stored documents could be used with a number of readout systems where these documents are printed out or displayed. The readout-only system nor-mally requires a lower power light source and no light modulator and is thus less expensive.
~115838 In many existing systems all of the information is written onto the disc at a single time interval without ever removing the disc and re-placing it. In these the registration of each newly written track with re-spect to the previously recorded tracks is reasonably accurate since there is no problem of concentricity. However, even in these systems, subtle warpage or other distortions of the disc between recording periods can cause problems. The newly recorded tracks can overlap previously recorded tracks, thus destroying information. This problem is avoided by increasing track spacing, thus reducing the storage capability.
This tracking problem is particularly aggravated in systems where the disc is removed and then replaced, as would be the case in the desirable versatile arrangements. Here the eccentricity caused by the replaced disc not being exactly centered again can cause the tracks to cross and destroy information. If guard bands are placed between recording intervals, much of the information storage capacity is lost.
This problem is solved by the unique approach illustrated in Fig-ure 2. Here the focused modulated light beam 42 is referenced to a prev-iously recorded track 41 so as to insure that the tracks maintain the de-sired spacing independent of eccentricity or distortion. Initially a refer-ence track is written on the outer periphery of the disc. This can be doneusing a lead screw to radially drive a light source while the disc is being rotated. A tracking light source, positioned a fixed radial distance with respect to the modulated light source, is used to track the reference track and thus position the writing beam. As new tracks are written, the tracking beam tracks those to accurately position the focused modulated light beam with respect to the previously recorded track.
In Figure 2 the modulated light beam 28 is produced by an argon laser source 12 and modulator 13. This beam is transmitted through di-chroic mirrors 51 and 43. These mirrors are transmissive to the shorter wavelength of the argon laser and reflective or partially reflective to the .f . ~
illS838 longer wavelength of the helium neQn laser 46 which is the source of the tracking light beam 52. The modulated light bea~ 28 is then reflected off controllable mirror 24 and focused by objective lens 40 onto the surface of rotating disc 10 to produce focused modulated light beam 42.
The tracking light beam 52 is reflected from dichroic mirror 51 and is partially transmitted by the partially reflective dichroic mirror 43. It is then also reflected off controllable mirror 24, at a slightly different angle, and focused by lens 40 to produce a focused tracking beam at track 41 which is displaced a fixed radial distance from the focused mod-ulated light beam 42. The light reflected from track 41 traverses the same optical path in the opposite direction and is partially reflected off par-tially reflecting dichroic mirror 43. This reflected beam is focused by lens 50 onto adjacent photocells 48 and 49. Their outputs are applied to difference amplifier 47. This amplifier subtracts the two photocell outputs to form error signal 53. This signal will be zero when the two outputs are equal which corresponds to the focused tracking beam being exactly on the previously recorded track 41. If it is off on either side, either photocell 48 or 49 will have a greater output, generating a positive or negative error signal 53. This error signal is coupled to the mirror actuator system 45 which drives rotator 44 and thus pivots mirror 24 in response to signal 53.
The mirror actuator system 45 can be a servo-amplifier with rotator 44 a servo-motor. As mirror 24 rotates the focused tracking light beam is brought onto the center of previously recorded track 41 and the focused modulated light beam 42 is simultaneously moved to remain a fixed radial distance from the focused tracking light beam. Thus the focused modulated light beam is kept a fixed radial distance from the previously recorded track.
The mirror 24, rotator 44 and objective lens holder 25 are all supported by pickup arm 26 of Figure 1. This pickup arm is moved radially by linear actuator 20 which provides the coarse radial motions which brings the tracking system into the vicinity of the correct track. The rotating lliS838 tracking mirror 24 has a range of a number of tracks so that the coarse radial position provided by linear actuator 20 needn't be very accurate.
The tracking light system can also be used in the readout mode without using the modulated light beam 28 from the argon laser 12. As the focused tracking light beam tracks the previously recorded tracks it is providing a readout of these tracks in addition to a tracking error signal 53. For example the output of either photocell, such as 48 as shown, can be used for the recording signal 29 which is then applied to the display system or printer 16. Alternatively, the sum of the two photocells 48 and 10 49 can be used for recording signal 29.
Assembly 25 in Figures 1 and 2 contains the objective lens 40 which must be kept a fixed distance from the surface of disc 10. This can be accomplished by an air bearing system such as the one desc~ibed in United States Patent 3,947,888 "Hydrodynamic Bearing Head Providing Constant Spac-ing" issued to Manfred H. Jarsen On March 30, 1976.
As shown in Figure 3, a number of methods may be used to redis-tribute the material in deformable film 31. Referring to the upper layers only and ignoring the lower layers, the incident energy causes the material in film 31 to become momentarily liquified. Due to phenomena such as sur-20 face tension the material redistributes itself in a new configuration whichcan be subsequently read out. With sufficient incident power the material in deformable film 31 will redistribute itself so as to form a void 33.
This can be read out in a number of ways. For example, the variation in light transmission can be measured by transmitting a focused readout beam through the film to a photocell on the other side of the substrate. Gen-erally, however, it is more convenient to have the readout beam measure var-iations in reflected light as shown in Figures 1 and 2.
The variations in reflection can be enhanced by the use of an ad-ditional antireflection coating 32 placed between the deformable film 31 and 30 the light source. Firstly, however, this film has an important function in 11~5838 the writing operation by matching the modulated light beam to the deform-able film 31. Anti-reflection coating 32 can provide matching by being a quarter wave thick at the writing wavelength and having a refractive index which is the geometric mean of that of free space and that of the deform-able film. Alternatively it can be a more complex multilayer coating. The film will thus minimize the reflections of the modulated light beam so that most of the energy goes into deformable film 31.
The coating 31 can serve a variety of functions in the reflective readout mode. For example it can minimize the reflections of the readout beam from the film, and result in large reflections in the vicinity of voids 33 because the coating 32 is intentionally not matched to the sub-strate material 30. Alternatively, when using a readout wavelength differ-ent from that of the writing beam, a relatively large reflection can be ob-tained at the metal film and a small reflection at the void since, at the readout wavelength, the coating 32 is better matched to the substrate 30 than the deformable film 31. Here the readout signal will have the opposite polarity since it will decrease in the written regions.
The power requirements are further diminished by having the modu-lated light beam liquefy only the upper portion of the film. Here the ma-terial will redistribute itself in the forms shown in 34 and 35. In 34 the material has redistributed itself into a concave region and in 35 it has become a concave diffuse region because of the material used. These are ~lso read out due to their varying reflectivity. This variation is due to combinations of effects. One effect is the partial destruction of the matching between anti-reflection coating 32 and the deformable film 31 due to the small separation. This causes increased reflections at the exposed regions. Another effect is the spreading of the reflected light caused by the concavity 34. This can cause an effective increase or decrease in re-flectivity depending on the remainder of the optical system. The lens action of the concavity can cause the reflected beam to be more or less lilS~38 concentrated on the receiving photocell as determined by the optics. The diffuse region 35 will, in general, cause a spreading of the light beam without lens action. This effect alone will result in an effective decrease in reflectivity.
It is important to note that the particular mode of operation is determined by the power level of the modulated light beam. To maintain this at its proper value, the newly written track can be immediately read out with the resultant signal used to control the power of the modulated light beam. The readout should be done at some information independent portion of the track, such as a portion corresponding to a synchronization region, which should always produce the same readout signal.
The ability to use the anti-reflection coating 32, with its many advantages is a result of the novel recording scheme used where the film ma-terial is redistributed by the modulated light beam. In the prior art, where high powers are used to vaporize the material, this coating could not be used since it does not permit the escape of the vaporized material.
As shown in Pigure 3, both sides of the disc can be used. An ad-ditional deformable film 31 and anti-reflection coating 32 is deposited on the underside of the substrate 30. This can be separately written on and read out in the same manner previously described to double the storage cap-acity of each disc.
In the systems discussed thusfar the writing modulated light beam itself caused the redistribution of material in the deformable film 31. An alternate embodiment is shown in Figure 4 where the modulated light beam acts as a control of another energy source which contributes to the process of redistributing the material in deformable film 31. Here a photoconductor 60 and a transparent conductor 61 are deposited on the deformable film 31.
If desired, these coatings can also have some of the anti-reflection proper-ties of coating 32 previously described. In addition, substrate 30 is made of conductive material. A power source 62 is connected between the trans-parent conductor ~1 and the conducting substrate 30. The modulated light beam 28, as before, is focused by objective lens 40 to form a focused spot 42 in the region of the photoconductive coating 60 and the deformable film 31. This focused modulated light beam changes the photoconductor from an insulator to a conductor, thus completing the electrical path in the vicin-ity of the focused light beam 42. This electrical energy is then applied to that region of deformable film 31 and contributes to the process of re-distributing the material of the film to create the writing action.
Although most of the embodiments illustrated used readout in the reflection mode, light transmission can also be used where the readout beam and photocell pickup are on opposite sides of the disc. This mode, how-ever, is limited to the redistribution arrangement 33 of Figure 3 where a void is created. It is also limited to recording the information on one side of the substrate 30.
Formats other than the disc format illustrated can be used with this system. The deformable film can be used in a rotating drum configura-tion with the light sources appropriately translated along the axis of the drum. Alternatively the deformable film can be used in a flat bed format where the light beams are mechanical or electro-optically scanned across the stationary deformable film. In all of the formats the tracking while writing can be accomplished by referencing to a previously recorded track as was de-scribed for the disc format.
The systems as described used the signal from a scanned document to modulate the writing light beam to produce the redistributions of mate-rail on the deformable film. The information used to modulate the light beam can, of course, be any signal source. One important application is the storage of digital information. Thus modulator 13 in Figure 1 can be driven by a digital signal derived from a computer. The signal 29 read out by de-tector 15 will then be the desired digital information.
The track format on disc 10 will generally be a spiral so that continuous information can be recorded over more than one track. In some applications, however, it may be convenient to use a concentric ring format.
In this case the linear actuator 20, rather than moving continuously, moves in radial steps following each revolution of disc 10.
Under some conditions disc 10 in Figures 1 and 2 may be subject to excessive vibration. Under those circumstances air bearing assembly 25 may not be able to adequately follow these variations, especially when they occur at a relatively high frequency. This problem is solved by the use of a forced air system, not shown, on the underside of the disc 10. This forced air can be derived from an annular array of apertures positioned under the disc. The air creates a force proportional to position which both reduces the amplitude and frequency of the vibration. In addition, it provides a viscous force which damps the vibration. These effects bring the variations within the range of air bearing assembly 25.
~ 7
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for recording information as variations in reflectance comprising: a metallic deformable film deposited on a substrate in a disc format; a modulated light beam represent-ing the information to be recorded focused onto the metallic deformable film having an intensity which is sufficient to liquefy but not vaporize the material of the metallic deformable film resulting in a redistribution of the material of the metallic deformable film which changes the reflectance of a readout light beam; and means for rotating the disc with respect to the modulated light beam and radially translating the modu-lated light beam to produce a pattern of recorded reflectivity information.
2. Apparatus as recited in claim 1 wherein the redistri-bution of material in the metallic deformable film results in partial removal of the material in the film in the region of the focused modulated light beam whereby the reflectance is changed with the minimum intensity of the modulated light beam.
3. Apparatus as recited in claim 2 wherein the redistri-bution of the material of the metallic deformable film results in a local concavity in the film in the region exposed to the modulated light beam.
4. Apparatus as recited in claim 2 wherein the redistri-bution of material of the metallic deformable film results in a local diffuse structure in the film in the region exposed to the modulated light beam.
5. Apparatus as recited in claim 1 or 2 wherein the means for radially translating the modulated light beam includes means for optically tracking a previously recorded track on the disc and radially translating the modulated light beam with respect to the previously recorded track.
6. Apparatus as recited in claim 1 or 2 wherein the metallic film is tellurium.
7. Apparatus as recited in claim 1 or 2 wherein the metal-lic deformable film is between 100 and 500 Angstroms thick.
8. Apparatus as recited in claim 1 or 2 including an anti-reflection coating on the illumination side of the metallic deformable film whereby the modulated light beam is efficiently coupled to the deformable film.
9. Apparatus as recited in claim 1 wherein the redistri-bution of the material of the metallic deformable film results in a void in the film in the region exposed to the modulated light beam.
10. Apparatus as recited in claim 9 including a coating which at the wavelength of the readout light beam is better matched to the metallic deformable film than the substrate whereby regions of the film containing voids result in increased reflections.
11. Apparatus as recited in claim 9 including a coating which at the wavelength of the readout light beam is better matched to the substrate than the metallic deformable film whereby regions of the film containing voids results in decreased reflections.
12. Apparatus as recited in claim 1 or 2 wherein the information used to modulate the light beam is derived by scan-ning a document and using the resultant scanned signal to pro-duce a frequency modulated signal to control the modulated light beam.
13. Apparatus as recited in claim 1 including means for reading the recorded information shortly after it is recorded to provide a signal which is used to control the power of the modulated light beam.
14. Apparatus as recited in claim 13 whereas the signal which is used to control the power of the modulated light beam is derived from portions of the recording which are independent of the information being recorded.
15. In a method for recording information as variations in reflectance thè steps of: modulating a light beam with the information to be recorded; focusing the modulated light beam on a metallic deformable film deposited on a rotating disc;
radially translating the modulated light beam with respect to the disc; and redistributing the material of the metallic deformable film in the region of the focused modulated light beam to change its reflectance with the modulated light beam having sufficient energy to liquefy but not vaporize the material.
radially translating the modulated light beam with respect to the disc; and redistributing the material of the metallic deformable film in the region of the focused modulated light beam to change its reflectance with the modulated light beam having sufficient energy to liquefy but not vaporize the material.
16. The method of claim 15 wherein the step of radially translating the modulated light beam includes the step of tracking a previously recorded track and translating the modu-lated light beam with respect to the previously recorded track.
17. The method of claim 15 including the step of scanning a document and using the resultant scanned signal to produce a frequency modulated signal for the recording information.
18. The method of claim 15 including the steps of: reading the recorded information shortly after it is recorded; and con-trolling the power of the light beam with a signal derived from the recently recorded information to establish the correct recording level.
19. The method of claim 15 or 18 wherein the step of redistributing the material of the metallic deformable film includes the step of removing only a part of the material from the metallic deformable film in the region of the focused modulated light beam.
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|---|---|---|---|
| US78105677A | 1977-03-24 | 1977-03-24 | |
| US781,056 | 1977-03-24 |
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| CA1115838A true CA1115838A (en) | 1982-01-05 |
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|---|---|---|---|
| CA299,591A Expired CA1115838A (en) | 1977-03-24 | 1978-03-23 | Information storage and retrieval system |
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| JP (1) | JPS53119005A (en) |
| AU (1) | AU520835B2 (en) |
| BR (1) | BR7801789A (en) |
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| GB (1) | GB1602893A (en) |
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| US4205339A (en) * | 1978-07-20 | 1980-05-27 | Eastman Kodak Company | Frame storage and retrieval wherein the frame fields are quadrature amplitude modulated on a single carrier |
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| USRE32431E (en) * | 1978-11-16 | 1987-06-02 | Discovision Associates | System for rotating an information storage disc at a variable angular velocity to recover information therefrom at a prescribed constant rate |
| US4229808A (en) * | 1978-12-21 | 1980-10-21 | Ncr Corporation | Method for recording multiple data segments on a storage disc with eccentricity factor |
| US4264986A (en) * | 1979-03-12 | 1981-04-28 | Willis Craig I | Information-recording process & apparatus |
| US4290122A (en) * | 1979-05-14 | 1981-09-15 | Xerox Corporation | Self-synchronizing clock source for optical memories |
| JPS5621893A (en) * | 1979-07-27 | 1981-02-28 | Xerox Corp | Optical recording part |
| US4268840A (en) * | 1979-07-27 | 1981-05-19 | Xerox Corporation | Optical recording member |
| JPS57208639A (en) * | 1981-06-18 | 1982-12-21 | Toshiba Corp | Recording method of disk |
| JPS58194149A (en) * | 1982-05-08 | 1983-11-12 | Asahi Optical Co Ltd | Information reader from optical recording carrier |
| CA1198209A (en) * | 1983-11-24 | 1985-12-17 | Northern Telecom Limited | Optical disc |
| JPS60236119A (en) * | 1984-05-09 | 1985-11-22 | Toshiba Corp | Optical information recording and reproducing device |
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| DE702967C (en) * | 1938-03-15 | 1941-02-20 | Ernst Bergmann | Method for recording and playing back optical sound recordings |
| US3365706A (en) * | 1964-04-15 | 1968-01-23 | Gilbert W. King | Photo-optical data storage and retrieval system employing error detection and error location identification components |
| FR1471797A (en) * | 1965-03-20 | 1967-03-03 | Bosch Gmbh Robert | Method and device for recording information |
| US3665483A (en) * | 1969-06-06 | 1972-05-23 | Chase Manhattan Capital Corp | Laser recording medium |
| US3774172A (en) * | 1972-03-23 | 1973-11-20 | D Silverman | Random access multiple disc optical information storage system |
| FR2212070A6 (en) * | 1972-08-25 | 1974-07-19 | Thomson Csf | |
| NL7212015A (en) * | 1972-09-04 | 1974-03-06 | ||
| NL174591C (en) * | 1973-02-09 | 1984-07-02 | Philips Nv | DISC REGISTRATION CARRIER BODY. |
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| NL165316C (en) * | 1973-10-01 | 1981-03-16 | Mca Disco Vision | METHOD FOR MANUFACTURING A WRITTEN VIDEO PRINTING DIES FROM A MOTHER'S DISC. |
| JPS50136051A (en) * | 1974-04-15 | 1975-10-28 | ||
| JPS5444524B2 (en) * | 1974-09-13 | 1979-12-26 | ||
| JPS5842527B2 (en) * | 1975-02-08 | 1983-09-20 | ティアック株式会社 | Disk Jiyouki Rokubaitaiheno Jiyouhoushingounokirokuhouhou |
| DE2522405C2 (en) * | 1975-05-21 | 1982-04-15 | Philips Patentverwaltung Gmbh, 2000 Hamburg | Multi-channel optical disk storage system for storing digital information |
| FR2366636A1 (en) * | 1976-10-01 | 1978-04-28 | Thomson Brandt | DEVICE FOR OPTICAL RECORDING OF INFORMATION ON A MEDIA WITH SLAVE OF THE POSITION OF THE RECORDING TASK ON THE INFORMATION MEDIA |
-
1978
- 1978-03-17 AU AU34232/78A patent/AU520835B2/en not_active Expired
- 1978-03-22 BR BR7801789A patent/BR7801789A/en unknown
- 1978-03-22 SE SE7803292A patent/SE438929B/en not_active IP Right Cessation
- 1978-03-23 NL NL7803200A patent/NL7803200A/en not_active Application Discontinuation
- 1978-03-23 FR FR7808506A patent/FR2385170B1/en not_active Expired
- 1978-03-23 CA CA299,591A patent/CA1115838A/en not_active Expired
- 1978-03-23 DE DE19782812886 patent/DE2812886A1/en not_active Ceased
- 1978-03-23 GB GB11767/78A patent/GB1602893A/en not_active Expired
- 1978-03-24 JP JP3321278A patent/JPS53119005A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6244333B2 (en) | 1987-09-19 |
| BR7801789A (en) | 1979-01-02 |
| FR2385170B1 (en) | 1985-08-09 |
| SE7803292L (en) | 1978-09-25 |
| GB1602893A (en) | 1981-11-18 |
| NL7803200A (en) | 1978-09-26 |
| AU3423278A (en) | 1979-09-20 |
| FR2385170A1 (en) | 1978-10-20 |
| SE438929B (en) | 1985-05-13 |
| DE2812886A1 (en) | 1978-10-26 |
| JPS53119005A (en) | 1978-10-18 |
| AU520835B2 (en) | 1982-03-04 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |