Page images
PDF
EPUB

p. 39).

of images containing a wide contrast of gray reader . . . which was designed specifically for scale because they are inherently low gamma and possible use aboard a manned space vehicle. The grain-free.” (Tauber and Myers, 1962, p. 409). reader would have a self-contained, fixed reference

6.46 "It is recorded that Alexander the Great file of up to 50,000 pages of information, such as discovered a substance, whose composition has navigational charts, planetary and space data, been lost in the obscurity of antiquity, that would and checkout, maintenance,

and

emergency darken when sunlight shone upon it. He dipped a procedures.” (Hanlon et al., 1965, p. 13). narrow strip torn from the edge of his tunic into "Current design emphasis by NCR has been a solution of the material and wore this strip toward the development of low cost PCMI readers wrapped about his left wrist. Many of his soldiers for commercial applications.” (Hanlon et al.,

, did the same. By observing the changes of color 1965, p. 19). during the day, they could tell the approximate

6.48 "The information glut threatening to swamp hour. This became known as Alexander's rag the engineer and the scientist is being eased by a time-band. (I am sorry that I cannot identify, and British organization called Technical Information hence cannot give proper credit to the author of on Microfilm. The medium of the 'message' is the this delightful footnote to history.)” (Smith, 1966, National Cash Register Company's PCMI process.

This makes possible the storage of over 3000 printed 6.47 “1. Photochromic films provide very high

pages of information on a single 4-by-6-inch transresolution with no grain.

parency. The system used by TIM enables the “2. Photochromic films permit the storage

engineer to locate the data he wants in a matter of images containing a wide contrast

of seconds. He simply selects the proper transof gray scale because they are in

parency and immediately locates the appropriate herently low gamma and grain-free.

page images with an NCR reader which displays “3. Photochromic films provide immediate

the selected pages on an illuminated viewing screen. visibility of the image upon exposure.

TIM points out that one of the most valuable sources No development process is required.

of information to engineers and scientists is manu4. Photochromic films provide both

facturers' literature. The problem has been that erasing

this is produced in an extraordinary variety of and

rewriting functions. This permits the powerful processes

forms. These are difficult to catalogue compreediting, updating, inspection, and

hensively and they also create an enormous bulk. error correction to be incorporated

The NCR-developed PCMI technology involves into systems.

a photochromic coating which produces an image “5. The PCMI process incorporates the

that is virtually grain-free. The process permits

a microscopic-size reduction which is not practical ability to effect a bulk-transfer read-out

with conventional microfilm processes. NCR is of micro-images at the 200:1 reduction level by contact printing.

producing the transparencies for TIM in its Dayton, “6. Use of high-resolution silver halide

Ohio processing center from 35-millimeter microfilms provides both permanency for

film supplied by the British firm. All data is updated the storage of micro-images and eco

every six months.” (bema News Bull., Dec. 9, 1968, nomical dissemination of duplicates.

6.49 "Information stored 7. The very high density of 200:1 micro

photochromic

coatings is semipermanent ... This is a result images offers the possibility of using

of the reversible nature of the photochromic coating. some form of manual retrieval tech

The life of the photochromic micro-image is deniques for many applications. This

pendent upon the ambient temperature of the coateliminates the normal requirement in

ing. At room temperature, image life is measured systems of this size for expensive and

in hours, but as the temperature is lowered, life complex random access hardware. (Tauber and Myers, 1962, p. 266).

can be extended very rapidly to months, and even

years." (Hanlon et al., 1965, p. 8). In the photochromic micro-image (PCMI) micro- 6.50 “The temperature-dependent decay of form process developed by the National Cash image life obviously prohibits the use of photoRegister Company there have been achieved chromic micro-images in their original form for "linear reductions from 100-to-l to greater than archival storage. To overcome this problem, means 200-to-1, representing area reductions from 10,000- have been developed for contact-printing the phototo-l to greater than 40,000-to-1, (which) have been chromic micro-images to high-resolution successfully demonstrated by using a variety of photographic emulsion, thereby producing image formats, such as printed materials, photo- permanent micro-images.” (Hanlon et al., 1965, graphs, drawings, and even fingerprints.” (Hanlon et al., 1965, p. 1).

“The entire contents of the photochromic micro"NCR has developed a number of research image plate are then transferred (as micro-images) prototype readers for viewing PCMI transpar- in one step, by contact-printing onto a high-resoluences ... [including) a miniaturized microimage tion silver halide plate . . . Micro-image dissemi

p. 8).

on

a

pp. 8–9).

nation (duplicate) films are prepared in a similar by 6 inches – can now be used to store a pattern manner, using the silver masters to contact-print of bits instead of images of pictorial or alphabetical onto high-resolution silver halide film." (Hanlon information. Photochromic high-resolution films et al., 1965, p. 9).

coupled with proper light sources and optical 6.51 Further, “a more realistic assessment systems can provide the storage of millions of bits so that spillover, halation, and registration restric- to the square inch. A micro-holographic indexing tions would not be impossibly severe, still results system used with such storage devices may revoluin a contiguous bit density of 10%/cm?.” (Reich and tionise data storage and retrieval." ("R and D for Dorion, 1965, p. 572).

Tomorrow's Computers,” 1969, p. 53). 6.52 “Transparent silicate glass containing 6.56 “The breadth of the sensitivity characsilver halide particles darkens when exposed to teristics of the photochromic films in conjunction visible light, and is restored to its original trans- with the width of the spectral characteristics of the parency when the light source is removed. These available phosphors present a potential systems glasses have been suggested for self-erasing memory designer with a choice of a number of component displays, readout displays for air traffic controls, parts . . Future improvements in CRT-photoand optical transmission systems. : .

chromic film display systems are dependent upon “Photochromic glass appears to be unique among the capabilities of each of the components. The other similar materials because of its non-fatiguing basic parameters which enter into the cathode characteristics. No significant changes in photo- ray tube efficiency are the fiber optic plate and chromic behavior have resulted from cycling phosphor. An increase in the fiber optic efficiency samples with an artificial 3600X black light source is doubtful except through the use of higher numeriup to 30,000 cycles. There were also no apparent cal aperture fibers. Increasing the numerical solarization effects causing changes in darkening aperture has the disadvantage of requiring a higher or fading rates after accelerated UV exposure degree of control on the film-CRT gap. An improveequivalent to 20,000 hours of noon-day sunshine."

ment in basic phosphor efficiency is difficult to (Justice and Leibold, 1965, p. 28).

foresee although several military agencies are “Another potentially important application of now or will be sponsoring programs to achieve photochromic materials is in the display of infor

this goal. mation. Data can be recorded in photochromic "An advance of the state-of-the-art of phosphor glass in two ways: by darkening the glass with short- technology should be possible by a factor of 4, wavelength light in the desired pattern; or by uni- but probably not beyond. By careful optimization formly darkening the glass and bleaching it, in the of the phosphor deposition with respect to particular desired pattern, with longer wavelength light." applications some improvement is possible. At (Smith, 1966, p. 45).

the same time an increase in the efficiency of the 6.53 “To produce a display, patterns of varying photochromic film by a factor of 2 is theoretically optical density are written on photochromic film possible. Of more importance to the system dewith a deflected ultraviolet light beam. The film signer is the understanding and optimization of so exposed forms the ‘object' in a projection system. writing and rewriting rates as they affect phosphor Visible light is projected through the film onto a efficiency and life and in the matching of the CRT screen. This display has mechanical simplicity, with the photochromic film." (Dorion et al., 1966, controllable persistence, and a brightness comparable to conventional film-projection displays." 6.57 “Wavefront reconstruction was invented (Soref and McMahon, 1965, p. 62).

by Gabor and expounded by him in a series of 6.54 “For dynamic applications such as target classic papers (1948–1951).” (Armstrong, 1965, tracking, this technique not only permits a real

p. 171). time target track, but also provides target track "The wavefront reconstruction method of image history in the form of a trace with 'intensity' formation was first announced by Gabor in 1948." decreasing with time. The time period covered by 6.58 Stroke gives a derivation of the term: the visible target track history is a function of “Hence, the name 'hologram' from the Greek the photochromic material. At the present time, roots for 'whole' and 'writing'." (Stroke, 1965, p. 54). the speed of photochromic materials limits the And also defines it: “A hologram is therefore an character generation rate to less than 100 characters interference pattern between a reference wave per second. Successful development of faster and the waves scattered by the object being rephotochromic materials will provide an attractive corded.” (Stroke, 1965, p. 53). electro-optical dynamic large-screen display with 6.59 See also the following: no mechanically moving parts." (Hobbs, 1966, “Arbitrary objects ... are

illuminated by p. 1879).

parallel laser light. In the general case, the light 6.55 "One of the technological trends which reflected by these objects will be diffuse and the will give us mass memories at a viable price is reflected wavefronts will proceed to interfere in photochromic microimagery. Photochromic tech- the photosensitive medium where the interference niques - by which as many as 2,000,000 words pattern can be recorded. After the photosensitive can be stored on a film transparency only 4 inches medium has been exposed and processed it is

p. 58).

are

[ocr errors]

p. 67).

[ocr errors]

as

an

called the hologram, which may be defined as the spatial frequency content or bandwidth of the recorded interference of two or more coherent device is available for the single image. Comwavefronts. When the hologram is illuminated by putationally, kinoform construction is faster than one of the original wavefronts used to form it, the hologram construction because reference beam remaining wavefronts

reconstructed

and image separation calculations are unnecessary. Observation of these reconstructed wavefronts is “A kinoform operates only on the phase of an nearly equivalent to observing the objects from incident wave, being based on the assumption that which they were originally derived.” (Collier, 1966, only the phase information in a scattered wave

front is required for the construction of an image “An optical hologram is a two-dimensional photo- of the scattering object. The amplitude of the graphic plate which preserves information about wavefront in the kinoform plane is assumed conthe wavefront of coherent light which is diffracted stant. The kinoform may therefore be thought of from an object and is incident upon the plate. A as a complex lens which transforms the known properly illuminated hologram yields a three- wavefront incident on it into the wavefront needed dimensional wavefront identical to that from the to form the desired image. Although it was first original object, and thus the observed image is conceived as an optical focusing element, the an exact reconstruction of the object. The observed kinoform can be used as a focusing element for image has all of the usual optical properties as- any physical waveform, e.g., ultrasound or microsociated with real three-dimensional objects; waves." (Lesem et al., 1969, p. 150). e.g., parallax and perspective.” (Lesem et al., 6.63 "A new hologram made at Bell Telephone 1967, p. 41).

Laboratories now allows the viewer to see a 3D 6.60 "Holography is the science of producing image rotate through a full 360 degrees as he moves images by wavefront reconstruction. In general his head from side to side . . . To make a flat no lenses are involved. The reconstructed image hologram with a 360-degree view, vertical strips may be either magnified or demagnified compared of the photographic plate are exposed sequentially to the object. Three-dimensional objects can be from left to right across the plate. A narrow slit reconstructed

three-dimensional images." in a mask in front of the plate allows only one (Armstrong, 1965, p. 171).

strip to be exposed at a time, each strip becoming 6.61 "Are Holograms Already Outdated? a complete hologram of one view of the object." Holography is one of the most exciting developments (Data Proc. Mag. 10, No. 4, 16 (Apr. 1968)). of today's technology. Holograms make use of a 6.64 “Holography provides alternative high-energy laser beam to store or display three- description of pictures, which might be more dimensional images for such applications as read- amenable to bandwidth compression. To investigate only storage; packing densities and device speeds this possibility, it is desirable to measure various are extremely impressive. However, at today's statistics of the hologram, and to try various operapace of innovation, holography may be outmoded tions on it to see what their effects would be on before it approaches being practical. One of the the reconstructed pictures. . . . Holography and latest competitors for 3-D display, storage, and wave other coherent optical processing ... techniques conversion applications is the kinoform, a new wave- have made possible relatively simple ways of obtainfront reconstruction device which also projects a ing the Fourier transforms of two-dimensional 3-D image, but requires one-fourth of the computer functions and operating on them in the frequency time to generate and creates images roughly three domain.” (Quarterly Progress Report No. 81, times as bright.

Research Laboratory for Electronics, M.I.T., "A computer program is used to produce a coded 199 (1966)). description of light being scattered from a particular

6.65 “Gabor and others have proposed the use object. The resultant computations are used to

of the wavefront reconstruction method to produce produce a 32-grey-level plot which is photoreduced

a highly magnified image, using either a change in and bleached. Then, when subjected to even a very small light source, such as the girl's earring

wavelength between recording of the hologram and

its reconstruction, or by using diverging light for in the photo above, the 3-D image is formed. A

one or both steps of the process. The two-beam kinoform image can be produced of any object which

process is readily amenable to such magnificacan be computer-described. Examples might include proposed buildings, auto designs, relief

tion ..." (Leith et al., 1965, p. 155). maps,

6.66 “Color reconstructions should be attainable or two-dimensional alphanumeric data." (Datamation 15, No. 5, 131 (May 1969)).

from black and white holograms if suitable temporal 6.62 “The kinoform is a new, computer-gener

coherence conditions are ensured." (Stroke, 1965, ated, wavefront reconstruction device which, like the hologram, provides the display of a three- “Holography is another field for which the laser dimensional image. In contrast, however, the has opened many possibilities. Perhaps it will illuminated kinoform yields a single diffraction find useful applications in pattern recognition and order and, ideally, all the incident light is used in storage of three-dimensional information as a to reconstruct this one image. Similarly, all the Fourier transform.

[ocr errors]

a

[ocr errors]

p. 60).

"Three-dimensional displays of airfield approaches in the cockpit of a jet liner with the correct viewing angle from the position of the aircraft would be a more interesting application of laserholographic recordings).” (Bloembergen, 1967,

а

p. 86).

[ocr errors]

“We read about images having three-dimensional properties, magnification obtained by reconstructing with a wavelength greater than that used in forming the hologram, diffuse holograms which, even when broken, produce whole images, multicolor images obtaining from emulsions which normally produce only black and whites." (Collier, 1966, p. 67).

“The recording of surface deformations in engineering components demonstrated here shows how these techniques may be applied at low cost and in a short time. For teaching purposes it has been shown that interference holography of the distortions of a rajor blade can be demonstrated adequately to a large group of people in only a few minutes." (Bennett and Gates, 1969, p. 1235).

“With practical applications for holograms still in the few-and-far-between stage, the Office of Naval Research and IBM believe they have a holographic application that is both practical and unique: in a head-up, all-weather landing system.

“ "The system - now at the laboratory model stage-employs a hologram of an aircraft carrier. The hologram is picked up by an infrared vidicon and projected on a crt cockpit display ...

“The achievement is one of application in which a two-dimensional representation with the socalled six degrees of freedom encountered in a carrier landing, and full ranging capability, is produced without employing a computer. The demonstration model simulates an approach window two miles wide and a half-mile high and offers a 3.5-degree glide slope. The six degrees (glide-slope deviation, localized deviation, depression angle, bearing angle, roll, and slant angle) are achieved mechanically, electronically, and optically. For example, roll is achieved as the vidicon itself is rolled; glide-slope deviation is simulated by manipulating the hologram. In the model, the generated image allows a view which includes magnification of the holographic image of the carrier up to 16-to-1 and permits views including one below the deck of the carrier.” (Electronics 42, No. 13, 46 (June 23, 1969).)

"General Electric has also examined the hologram for potential in character recognition. One method suggested by GE is to create a spatial filter using a hologram. This filter can be used to detect, or recognize, specific shapes from among a random assortment.

“This general scheme is the basis for a personnel identification system being developed by National Cash Register Co., Dayton, Ohio.

"According to NCR, two of the most important aspects of identification are signatures and photo

graphs. In the NCR system, a hologram containing signatures and numbers randomly located is placed in the optical path of a laser.

"If matching occurs when a signature card is inserted into a receiving device, the system locates the picture (which] is projected for comparison.” (Serchuk, 1967, p. 34).

6.67 "The wavefront reconstruction method offers the possibility of extending the highly developed imagery methods of visible-light optics to regions of the electromagnetic spectrum where high-quality imagery has not yet been achieved ..." (Leith et al., 1965, p. 157).

6.68 "A Megabit digital memory using an array of holograms has been investigated by Bell Laboratory scientists. The memory is semipermanent, with information being stored in the form of an array of holograms, each hologram containing a page of information. A page is read ... by deflecting a laser beam to the desired element of the array, so as to obtain reconstruction of the image stored in the element - the digital information -on a read-out plane which is common to all elements of the array. Photosensitive semiconductors arrayed on the read-out plane then sense the stored information .

"In the Bell Labs experimental system, the light source is a continuous-wave helium-neon laser operating in the lowest order transverse mode. Two-dimensional deflection is accomplished by cascaded water-cell deflectors, using Bragg diffraction from ultrasonic waves in water, and capable of deflecting the beam to any of 300 addresses in less than 15 usec

“The present system comprises 6 k bits per page, and a 16 x 16 matrix of pages, for a total capacity of 1.5 M bits access time is 20 usec. Total optical insertion loss is 75 db, resulting in 70 k photons impinging on each bit detector.

each bit detector . . . and Bell Labs scientists project that, by straightforward extensions of the present system, 25 M bits with an access time of 7 usec is a feasible system. This system would have 65 x 65 matrix of 6 k bit pages, a faster deflection system, and a reduced insertion loss of 65 db, resulting in 0.5 M photons per bit at the detectors.

“Ultimately, it is predicted that a memory can be built having greater than 100 million bits of storage, with an access time in the one microsecond range." (Modern Data Systems 1, No. 2, 66 (Apr. 1968).)

“Bell Labs has already constructed a 'breadboard' hologram memory system . . . that may eventually be able to display any one of 100 million units of information upon one millionth of a second's notice.

"It is based on using a number of closely spaced holograms on a single photographic plate. Bell Labs had in mind switching operations as one fundamental application

“This memory system works by directing a laser

[ocr errors]

*40

beam to one 'page' (location of a hologram) in an array. Initial goals are to make each hologram about a millimeter in diameter and to space them rather closely in a pattern of 100 rows by 100 rows. Each hologram will store, encoded in the form of an interference pattern, another 100 by 100 matrix. This will be coded in dots or blanks to represent information. The reconstructed hologram will be aligned precisely with an array of phototransistors (also under development at Bell Labs), which will ‘report' to the electronic device which of the dots are present and which are absent. This roll call is the message." (Photo Methods for Industry 12, No. 3, 61-62 (Mar. 1969)).

6.69 “Carson Laboratories, Bristol, Conn., for example is working on the development of potassium bromide and similar crystals as holographic materials.

“The laser is used to bleach the crystal in accordance with the holographic interference patterns. Such a memory device is said to have a capacity of 1 million bits per square half-inch of material." (Serchuk, 1967, p. 34).

6.70 “An experimental optical memory system that could lead to computer storage devices a thousand times faster than today's disk and drum storage units was reported ... by three International Business Machines Corporation engineers.

“In the experimental system, blocks of information are accessed by a laser beam in just tenmillionths of a second. More than 100 million bits of computer information could be stored on a nine square inch holographic plate ...

"The experimental memory system uses a laser beam to project blocks of information contained on the hologram onto a light-sensitive detector. The detector then converts the projected hologram into electronic signals which can be processed by a computer.

"In a feasibility model, assembled at IBM's Poughkeepsie, N.Y., Systems Development Division Laboratory, size, direction, and focus of the laser beam are determined by a series of lenses. The beam is positioned on the hologram by a crystal digital light deflector. By controlling the polarization of the light from the laser the deflector is used to select any block of information stored on a single plate.

"The hologram splits the laser beam into two separate rays: one non-functional and the other a first-order diffraction pattern which carries the holographic information. This first-order diffraction pattern is then focused on a light-sensitive detector array, which converts the optical information to electronic signals. The signals, representing data, are then sent to the computer's central processing unit at high speeds.” (bema News Bull. 5, Nov. 18, 1968).

6.71 An advantage of storing information in the form of a hologram rather than as a single real image is that the loss of data due to dust and film defects is minimized, since a single bit is

stored not on a microscopic spot on the film but as part of an optical interference pattern which is contained in the entire hologram.” (Modern Data Systems 1, No. 2, 66 (Apr. 1968).)

“A bad spot in a photographic image will not spoil all bits of information completely; the Fourier transform of such a plate will still give a good image.” (Bloembergen, 1967, p. 86).

“Since information from any one bit of the object is spread out over the whole hologram, it is stored there in a redundant form, and scratches or tears of the hologram make only a minor deterioration in the overall reconstructed image. In particular, no single bit is greatly marred by such damage to the hologram." (Smith, 1966, p. 1298).

“Leith reports that diffused illumination holograms have an immunity to dust and scratches and that particles have little effect in producing erroneous signals as in previous photographic memories." (Chapman and Fisher, 1967, p. 372).

“Since light from the point source is spread over the entire hologram's surface (thus ensuring interference patterns over the entire film surface), any part of the hologram will reproduce the same image as any other part of the hologram. It can be seen that the only effect of dust and scratches is to reduce the active area of the hologram." (Vilkomerson et al., 1968, p. 1199).

“Generally, the light projected into an image by a hologram is not associated with any specific point of the hologram, thus, if the hologram becomes marred by dust or scratches there is little degradation of any one point in the image. Dust and film imperfections can be a severe problem in nonholographic storage, because errors arise from the degradation of specific bits." (Gamblin, 1968,

[ocr errors]

pp. 1-2).

as

6.72 Further, "the results of this study have indicated that holographic techniques are particularly suited to satisfy the functional requirements of read-only memory . . . Holography offers solutions to two key problems associated with the requirement for a single removable media storing up to 160,000 bits. First, the unique redundance inherent in holograms constructed with diffused illumination eliminates the loss of data due to such environmental effects dust and scratches. Second, the potential freedom from registration effects which can be achieved by proper selection of construction techniques allows the manual insertion and removal of media with high bit packing densities and does not add a requirement for complicated mechanical positioning or complex electrical interconnection in the read unit.” (Chapman and Fisher, 1967, p. 379).

6.73 "One can construct computer techniques which would take an acoustic hologram (the wavefront from a scattered sound wave) and transform it into an optical hologram, thereby allowing us to construct the three-dimensional image of the scatterer of the sound waves.' (Lesem et al., 1967, p. 41).

« PreviousContinue »