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study was the conclusion that lasers are capable of satisfying all the requirements for digital devices. It was shown that, in addition to the neuristor-type logic, lasers in form of resonators and amplifiers can have input-output characteristics that resemble those of conventional logic circuits such as gates or flipflops." (Reimann, 1965, pp. 250-251).
“Fiber-optic elements, with appropriate concentrations of active emissive ions and passive absorptive ions, are the basic components of this system. The computer is powered by being in a continuous light environment that provides a constant pump power for maintaining an inverted population of the emissive ions. Among the potentially attractive features of such a system are the freedom from power-supply connections for individual circuits, the possibility of transmission of signals without actual connections between certain locations, and a promise of high-speed operation.” (Reimann and Kosonocky, 1965, p. 182).
6.16 “The feasibility of machining resistive and capacitive components directly on thin film metallized substrates with a laser has been demonstrated. Tantalum films can be shaped into resistor geometries and trimmed to tolerance by removing metal. These films also can be oxidized to value using the laser beam as the heat source. Resistors can be made with tolerances in value of less than +0.1 per cent. ...
"Pattern generation by laser machining has been demonstrated on various thin films as well as on electroplated films. Vaporized lines as fine as 0.25 mil are readily attainable in thin films, as are 0.4 mil lines in plated films. Much narrower lines may be obtained under particularly wellcontrolled conditions. Uniform lines as fine as 1 micron have been scribed in thin films on sufficiently flat substrates. These films have been removed with minimum effect to the substrate surface." (Cohen et al., 1968, p. 403).
"Semiconductor laser digital devices offer an improvement in information processing rates of one to two orders of magnitude over that expected from high-speed integrated transistor circuits. Data processing rates of 10 to 100 gigabits per second may be possible using semiconductor lasers. However, the technology for fabricating low-power laser circuits is still undeveloped and low-temperature operation may be required." (Kosonocky and Cornely, 1968, p. 1).
“Laser digital devices may be used for generalpurpose logic circuits in very much the same way that transistors are now used, except that all of the processing is done with optical rather than electric signals.” (Reimann and Kosonocky, 1965, p. 183).
"Semiconductor current-injection lasers are most attractive for digital devices because of their small size, high pumping efficiency, and high speed of operation.” (Reimann and Kosonocky, 1965, p. 194).
“The utility of a laser as a tool for fabricating thin
film circuits results primarily from the spectral purity and degree of collimation of the laser light. These characteristics allow the beam to be focused to a very fine and intense spot. The high heat flux which occurs when the light is absorbed by the target material, and the sharp definition and localized nature of the working region allow heating, melting, or vaporizing minute amounts of material, with minimum effect to adjacent material or components.” (Cohen et al., 1968, p. 386).
6.17 See Hobbs, 1966, p. 42.
6.18 “A new laser data storage/retrieval system that provides a 1000-time increase in packing density over conventional mag tape, an error rate of 1x 108 better, permanent (nonerasable) storage, a transfer rate of 4 megabits/sec., and instantaneous read-while-write verification has been developed by Precision Instrument Co., Palo Alto, Calif.
“A working demonstrator of the 'Unicon' system uses a l-watt argon gas laser, which makes a hole in the metallic coating of a mylar-base tape wrapped around a drum. The current system, using 5-micron holes, offers a packing density of 13 million bits/sq. in.
“Readout is accomplished by reducing the laser power; beam reflection or non-reflection indicates nonholes or holes. The tape being used on the current system offers storage equivalent to 10 2400-ft. reels of 800 bpi tape. The system can serve on- and off-line, and is capable of recording analog, FM or video data, all of which require high speed." (Datamation 14, No. 4, 17 (Apr. 1968)).
6.19 “By early 1968, Precision Instrument Co. had developed a massive-scale laser recorder/ reader storage system, but the first order for the device was not received until this year. Ed Gray, the chief engineer on the UNICON (Unidensity Coherent Light Recorder/Reproducer) Laser Mass Memory System, said that convincing the first potential customers that they should acquire a $500K to $1 million memory system was not easy, especially when you had to 'tell someone that you were not going to store data with magnetics like God intended.' Now that the first order has been placed, by Pan American Petroleum Corp. of Tulsa, Oklahoma, Mr. Gray feels that the systems will move a little faster in the marketplace.
“The $740K system placed with Pan American is to be installed with all requisite software about March of 1970. Four other potential customers, including some government agencies and a private credit-reporting firm, are also expected to place orders." (Datamation 15, No. 3, 116 (Mar. 1969).)
6.20 "The National Archives and Records Service has begun a cost-effectiveness study of archival storage systems in an effort to shrink its mag tape library, which contains one million plus reels. The study, due for completion next month, is using the capabilities of Precision Instruments Unicon device as a model. The Unicon employs a
laser-etched aluminum strip with a 30-year shelf life.” (Datamation 14, No. 10, 171 (Oct. 1968)).
6.21 “Honeywell scientists are investigating a method that uses a laser for mass storage and retrieval of information in computer memory. Although emphasizing that development is still in the research stage and may be several years away from practical application, the researchers believe the discovery is a possible key to inexpensive mass storage of data for the enormous computer networks envisioned for the 1970's. (Commun. ACM 11, 66 (Jan. 1968)).
6.22 “The system ... uses a modulated laser beam to inscribe data onto photosensitive discs . . Each disc contains 3, 100 tracks with a capacity of 67,207 bits per track, including error corrections bits. The storage unit holds 2, 600 discs, stored on edge, in four (or eight] trays ... two auxiliary disc banks can be added to achieve the maximum memory capacity . of 150 billion characters. The reader reaches any piece of information on the 3, 100 tracks (per disc) within 15 milliseconds ...” (Business Automation 12, No. 6, 84 (1965)).
A CW helium-neon laser is used to "achieve real-time writing of information on the system's photosensitive memory discs." (Connolly, 1965,
“Such a system could be used with a matrix containing alphabetical or other symbols. The laser would be used as a print-out device, projecting the various symbols onto a recording medium.
"The Air Force Systems Command at WrightPatterson AFB is interested in IBM's work on a variable frequency laser which might be used in conjunction with
color-sensitive computer. This type of setup is said to have a potential capacity of a hundred million bits per square inch of photographic material.” (Serchuk, 1967, p. 34).
p 6.25 "Instead of recording a bit as a hole in a card, it is recorded on the file as a grating pattern of a certain spacing . . . A number of different grating patterns with different spacings can be superposed and when light passes through, each grating bends the light its characteristic amount, with the result that the pattern decodes itself . The new system allows for larger areas on the film to be used and lessens dust sensitivity and the possibility of dirt and scratch hazards." (Commun. ACM 9, No. 6, 467 (June 1966).)
6.26 “Recently Longuet-Higgins modeled temporal analogue of the property of holograms that allows a complete image to be constructed from only a portion of the hologram. In the present paper a more general analogue is discussed and two two-step transformations that imitate the recording-reconstruction sequence in holography are presented. The first transformation models the recall of an entire sequence from a fragment while the second is more like human memory in that it provides recall of only the part of the sequence that follows the keying fragment.” (Gabor, 1969, abstract, p. 156).
6.27 “A new recording mechanism ... sists of the switching of magnetization under the influence of a stress resulting from a heat gradient introduced by a very narrow light or electron beam. The mechanism is assumed to be magnetostriction with a rotation of the anisotrophy. The model presented and the criteria for recording are supported, at least in part, by experimental observations. (Kump and Chang, 1966, p. 259).
6.28 “In attempts to provide computers with previously unavailable amounts of archival (readonly) storage, various techniques involving optical and film technology have been employed to utilize the high information capacity of film (approximately 106 bits/in. ?) and the high resolution and precision of lasers and electron beams. The trillion-bit IBM 1350 storage device, an offshoot of the 'Cypress' system, . uses 35 mm x 70 mm silver halide film 'chips.'
“A total of 4.5 million bits are prerecorded on each chip by an electron beam. For readout, a plastic cell containing 32 film chips is transported to a selector, which picks the proper chip from among the 32; average access time to any of the 1012 bits is 6 seconds. After a chip is positioned, information is read using a flying-spot CRT scanner.
6.23 “A method for producing erasable holograms may enable an optical memory to store 100 million bits in a film one inch square.
“The memory could be read out, erased and reused repeatedly, according to Dr. William Webster, vice president in charge of RCA Labora. tories.
"Information can be written into the magnetic film in 10 billionths of a second, and erased in 20 millionths of a second. Laser light split into two beams, one going directly to the film and the other going to the information bit pattern, interferes constructively to produce heat and consequently a realignment of atoms.
"Where the two beams interfere destructively, nothing happens.” (Data Proc. Mag. p. 21 (Sept. 1969)).
6.24 In the IBM-laser system developed for Army Electronics Command and installed at Fort Monmouth, it is noted that: “Through employment of a deflection technique, the shaft of light can be focused on 131,072 distinct points within a space smaller than a match head. ... To provide a readout in printed form, the laser beam can scan through a mask inscribed with the alphabet and other symbols and through the action of light-bending (deflection) crystals - turn out the final product on photo-sensitive paper.” (Commun. ACM 9, 467 (1966)).
"At International Business Machines Corp. . .. one method, devised for the Army Electronics Command, Fort Monmouth, N.J., makes use of a high-speed switching arrangement with electronically controlled crystals.
Two IBM 1350 units are scheduled for mid-1967 delivery to the Atomic Energy Commission at Livermore and at Berkely for use with bubble chamber data. Other techniques of reading and writing with electron beams are explained by Herbert." (Van Dam and Michener, 1967, p. 205).
6.29 “Results of basic theoretical studies conducted at the NCR research laboratories have indicated that CW lasers of relatively low power should be capable of permitting very high resolution real-time thermal recording on a variety of materials in the form of thin films on suitable substrates. Subsequent laboratory studies have shown that such thermal recording is indeed possible. This recording technique has been termed heat-mode recording." (Carlson and Ives, 1968, p. 1).
“The recording medium is coated on a 5. by 7-inch glass plate, a quarter of an inch thick. The plate carrier mechanism is capable of stepping in the horizontal and vertical directions to form matrices of up to 5,000 images at an overall reduction of 150 to 1." (Carlson and Ives, 1968, p. 5).
“The results of the studies described in this paper have established laser heat-mode recording
a very high resolution real-time recording process capable of using a wide variety of thin film recording media. The best results were obtained with images which are compatible with microscope-type optics. The signals are in electronic form prior to recording and can receive extensive processing before the recording process occurs. In fact, the recordings can be completely generated from electronic input. For example, Figure 6 shows a section of a heat-mode microimage with electronically generated characters, produced by the Engineering Department in our Division. The overall image is compatible with the 150-to-1 PCMI system (less than 3 mm field), and consists of 73 lines of characters, 128 characters per line. Although this image was recorded in 1.6 seconds, faster recordings are anticipated. A description of this work will be published in the near future. (Carlson and Ives, 1968, p. 7).
6.30 “Another scheme for storing digital information optically is the UNICON system, under development at Precision Instrument Company. This system
a laser to write 0.7-microndiameter holes in the pigment of a film. Information is organized in records of at most a million bits; each record is in a 4-micron track extending about a meter along the film. Individual tracks are slanted slightly so that they extend diagonally across the film. (The amount of slant and the width of the film determine the length of the records.) Each record is identified by information stored next to the beginning of that record, in an additional track at the edge of the film. Readout of a particular record involves scanning the identifier track for the proper code and then scanning the track with a laser weaker than that used for writing. It is predicted, on the basis of an experimental working
model, that one UNICON device with 35 mm film could store a trillion bits on 528 feet of film, with an average access time to a record of 13 seconds." (Van Dam and Michener, 1967, p. 205). (See also note 6.14).
6.31 “Considerable experimentation in modulation and transmission is needed before optical communication by laser can be said to be really useful except in very specialized cases." (Bloom, 1966, p. 1274).
6.32 "At first sight a laser communication system with its extremely wide information carrying capacity would appear to be a natural choice for an interplanetary communication system. However, among other things, the acquisition and tracking problems are considered to be so severe that such a system is not thought to be realistic at the present time. This may be indicative of an information technology utilization gap.” (Asendorf, 1968, p. 224).
6.33 "In general, earthbound laser-ranging systems are limited by local atmospheric conditions. A typical value of range routinely measured is 20 km or less." (Vollmer, 1967, p. 68).
"Earthbound applications of coherent optical radiation for communications appear to be severely limited for two reasons. The first, and most significant, is the effect of atmospheric turbulence on the coherence of the radiation. The second is the effect of small vibrations on the coherent detection efficiency and signal-to-noise ratio. This can be minimized by careful design, but the first factor is beyond the designer's control. Although coherent optical detection has been demonstrated over some useful paths, the vulnerability of the link to atmospheric variations makes practical application somewhat doubtful.” (Cooper, 1966, p. 88).
6.34 “Is the enormous increase in bandwidth offered by light as a carrier frequency in communications needed? For transmission in space the acquisition and aiming of the light beams pose formidable problems. In the atmosphere, rain, smog, fog, haze, snow, etc., make light a poor competitor of microwaves. Can a system of enclosed tubes with controlled atmosphere and light repeater stations be built on a technologically sound and economically feasible basis?” (Bloembergen, 1967, p. 86).
6.35 “Information Acquisition, Sensing, and Input", Sect. 3.1.1. Some additional references are as follows:
“Since the first laser was demonstrated in 1960, considerable interest has developed in its possibilities for use in communication systems. The basic sources of this interest are the coherent nature of the radiation obtained as compared with all previously known extended sources of optical radiation, and the laser's short wavelength. This latter characteristic provides the potential ability to achieve bandwidths, or information capacities, that are orders of magnitude greater than anything obtained heretofore. A more realistic advantage, in terms of presently available information sources,
results from the combination of high coherence and similar receiving and recording station there short wavelength. It is the ability to generate a reconstructs the photographs to their original form highly collimated beam (limited by diffraction for immediate inspection." (Spie Glass 5, No. 2, phenomena), which leads to the ability to achieve 9 (Aug. 1969).) communications over great distances. Of equal "According to Air Force officials, pictures proimportance is the fact that with a coherent signal, duced by the CBS Laboratories Image Scanning coherent detection of the information can be and Recording System contain the highest resoluobtained with greatly improved immunity to natural tion ever reported in the transmission of aerial incoherent noise sources such as the sun.” (Cooper, reconnaissance photographs. High-altitude photo1966, p. 83).
graphs processed by the system show such detailed "The first enthusiastic suggestions that laser information as identification numbers of ships in technology potentially provides many orders of port, planes on runways and troop movements ... magnitude more communication capability than "In operation, the lightweight system uses a preRF technology, and that it might, therefore, offer cisely controlled laser beam to scan rapidly across the only solution to the problem of general wideband photographic film. The laser converts each picture communications with deep-space probes, needs frame to an electronic video signal. The signal is to be more carefully assessed." (Dimeff et al., then fed to a transmitting device for satellite relay, 1967, p. 104).
said John Manniello, CBS Laboratories Vice "For deep-space, wide-band communication . President for Government Operations, who conanother factor may be ... important - namely, the ceived the system application. Once the signals size of the transmitting aperture. A very large contact the satellite, they are flashed to a receiving aperture, as would undoubtedly be required by a station in Washington within seconds, he added. microwave channel, is likely to prove an obstruction “The receiving station - which has related phototo the sensors of the aircraft and will, therefore, scanning, recording and developing equipment reduce the time available for collecting information reconstructs the video signal to the original film or transmitting it. In this respect, the laser has an image and produces high-quality photographic important advantage over microwave.” (Brookner prints. et al., 1967, p. 75).
"Because of the laser-scanning technique in"Several optical links which use GaAs injection volved, no photographic resolution is lost between lasers as transmitters have been constructed. One recording and transmission from the original of them has been demonstrated to be capable film taken in Vietnam." (Spie Glass 5, No. 2, 9 of transmitting 24 voice channels over 13 km." (Aug. 1969).) (Nathan, 1966, p. 1287).
6.38 “Superficially, it appears attractive to have 6.36 "If we classify our communication require- fast switching, high storage density, direct visual ments on the basis of range, we find that lasers can display. Such developments would depend heavily be helpful at the range extremities – that is, for on the availability of cheap, small, high-quality distances less than about 15 km and for those semiconductor lasers. If these were available, the greater than 80 million km." (Vollmer, 1967, p. 66). entire organization of computers using them would
6.37 “An electronic system that transmits probably be different." (Bloembergen, 1967, p. 86). military reconnaissance pictures from Saigon to 6.39 “The power and efficiency available from Washington in minutes via satellite may soon lasers at the desired wave lengths (particularly enable news media to dispatch extremely high- ultraviolet) must be improved, and adequate laser quality photographs and type around the world deflection techniques must be developed before for instant reproduction.
laser displays will be feasible for widespread use." "Potential benefits are also foreseen for medicine, (Hobbs, 1966, p. 1882). earth resources surveys and industry.
“Since lasers don't require vacuums, there is “The high-performance system was developed a significant convenience relative to electron for the U.S. Air Force Electronics Systems Divisions beams. But there is a severe penalty compared to by CBS Laboratories, a division of Columbia electron beams due to problems in deflecting, Broadcasting System, Inc. It combines electro- modulating, and focusing." (Gross, 1967, pp. 7-8). optical and photographic techniques to relay high- “Lasers offer great promise for future impleresolution aerial photographs of ground activity mentation of display systems – particularly largein Vietnam to the President and Pentagon officials. screen displays. The ability of a laser to deliver Pictures seen by the President are many times highly concentrated light energy in a coherent beam sharper than the best pictures shown on home of very small spot size is well known. Several diftelevision sets.
ferent approaches to laser displays are being in“Within minutes after photographs have been vestigated. Since they all require some means for taken in Vietnam, they are readout by the system's deflecting and modulating the laser beam, conelectronic scanning device and converted to siderable development efforts are being expended video signals. The signals are then fed to a com- on deflection techniques. Digital deflection of munication link, which relays them over the U.S. lasers by crystals has been satisfactorily demonDefense Satellite Network to Washington. A strated for 256 positions in each direction, but at
least 1024 positions in each direction are needed and under a de-activation condition and/or at a for a practical large-screen display system.” (Hobbs, later time.” (“Investigation of Inorganic Photo1966, p. 1881).
tropic Materials ...", 1962, p. 1). “The laser is an efficient light source, and its “The property of certain dyes and other chemical output can be focussed to small sizes and high compounds to exhibit a reversible change in their power densities. There is confidence that laboratory absorption spectrum upon irradiation with specific means for modulating lasers and deflecting their wavelengths of light has been termed phototropism, beams will be found practical.” (Bonn, 1966, p. or photochromism. The emphasis in this definition 1869).
is on reversibility, because, upon removal of the “More rapid progress would be made in utilizing activating radiation the systems must revert to laser recording if better means of deflecting laser their original states to be considered photochromic." beams at the desirable speeds and resolutions (Reich and Dorion, 1965, p. 567). existed or were clearly foreseeable." (Smith, 1966, "By definition, photochromic compounds exhibit
reversible spectral absorption effects-color “An experimental device that can switch the changes, resulting from exposure to radiant energy position of a light beam more than a thousand in the visible, or near visible, portions of the times faster than the blink of an eye could become spectrum. For example, one class of photochromic an important part of computer memories of the materials consists of light-sensitive organic dyes. future. The device, a digital light deflector, was NCR photochromic coatings consist of a molecular developed at the IBM Systems Development dispersion of these dyes in a suitable coating Div. laboratory in San Jose, Calif.
material. Photochromic coatings are similar to “The experimental deflector changes the location photographic emulsions in appearance and with of a beam in 35 millionths of a second by a unique respect to certain other properties. Coatings can method of moving a glass plate in and out of contact be made to retain two-dimensional patterns or with a prism.
images which are optically transferred to their “High-speed deflectors of this type are poten- surface." (Hanlon et al., 1965, p. 7). tially useful in future optical memories to randomly "Photochromic film, a reusable UV sensitive position a laser beam for data recording and reading. recording media has progressed to the point Such beam addressable memories are expected where prototype equipment is being designed." to be many times faster than present magnetic (Kesselman, 1967, p. 167). storage methods because of the relative speed 6.43 “Photochromic coatings exhibit excellent of relocating a light beam in comparison to moving resolution capabilities. In addition, both positivea bulky recording head.” (Computers & Automation to-negative and direct-positive transfers are pos18, No. 5, 68 (May 1969).)
sible . . . The coatings are completely grain-free, 6.40 “Another attractive approach is the use of have low gamma (excellent gray scale characterisa laser beam to write directly on a large luminescent tics), and exhibit inherently high resolution screen. This is somewhat equivalent to an ‘outdoor' Further, because the coatings are reversible, the cathode-ray tube in which the laser beam replaces information stored can be optically erased and the electron beam and the luminescent screen rewritten repeatedly.” (Hanlon et al., 1965, p. 7). replaces the phosphor face plate of the tube. “Photochromism may be defined as a change in It offers advantages over a CRT in that a vacuum color of a material with radiation (usually near is not required and a large-screen image can be ultraviolet) and the subsequent return to the generated directly. One feasibility system has been original color after storage in the dark. Reversible developed using a 50 milliwatt neon-helium gas photochromism is a special case of this phenomenon laser, a KDP crystal modulator, a piezoelectric in which a material can be reversibly switched by crystal driven horizontal deflecting mirror, and a
radiation between two colored states. Photochromic galvanometer driven vertical deflecting mirror to compounds may be valuable for protection from provide a television rastor scan image projected radiation; reversibly photochromic materials are onto a 40 inch screen. Brightness of 50 foot-lam- potentially valuable for data storage and display berts, contrast ratio of 100 to 1 (dark environment), applications." (Abstract, talk on photochromic resolution of 1,000 to 2,000 lines, and update time materials for data storage and display, by U. L. of 33 milliseconds are anticipated for direct view Hart and R. V. Andes, UNIVAC Defense Systems laser systems." (Hobbs, 1966, p. 1882).
Division, at an ONR Data Processing Seminar, 6.41 "Electron-beam devices, including those May 4, 1966, See also Hart, 1966). which use photographic emulsions and thermo- 6.44 “Most of the systems so far reported are plastic films, operate in a vacuum, which is a only partially, or with difficulty, reversible, or are nuisance." (Bonn, 1966, p. 1869).
subject to fatigue-a change in behavior either 6.42 “By definition, phototropy is the photo- with use or with time in storage.” (Smith, 1966, chemical phenomenon of changing some physical property (color) on exposure to electromagnetic "Organic photochromic materials fatigue with radiation (light) and returning to its original (color- use.” (Bonn, 1966, p. 1869). less) state after removal of the activating source
6.45 "Photochromic films permit the storage