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Joseph Bordogna

Moore School of Electrical Engineering

University of Pennsylvania

Philadelphia, Pennsylvania 19174


Abstract: The pedagogic potential of RCA's HoloTape Video Playback System is assessed within the context of present innovative educational trends.


In education, particularly higher education, there is an urgent need for curricular innovation aimed at adapting teaching techniques to current needs [1]. On an international scale, present trends for change are based on a desire to provide learning centers capable of serving a larger segment of the public [2]. The design of such centers is intended to permit a variety of learning experiences over periods of tine commensurate with each individual's intellectual and social maturity as well as the time one can allot to furthering his education. Thus, for some students, the time to achieve degree status can be shortened, total tuition thereby reduced, and the full responsibility of adult life experienced at an earlier age. For others, the educational experience can be spread over a time period during which contributions can be made to society simultaneously.

To accomplish these innovations soinc of the traditional university teaching methods may have to be altered radically. At the very least, the present formal lecture methods should be modified to encourage learning at individual rates;

teachers should be able to respond quickly to a variety of individualized demands on their time; and evaluation of individualized progress should be clear-cut. Such a shift to more individualized service in the face of rising enrollments and costs suggests that institutions of higher learning make efficient use of modern technological aids in order to realize flexibility [3,4]. Those aids which offer greatest potential in this regard derive from computer and communication technologies - the computer as the key element in the management, alteration, and retrieval of information; communication systems for dissemination of this information. Various forms of computer-assisted instructional systems [5,6,7] and ITFS (Instructional Television Fixed Service) broadcast television systems [8,9] are in operation. Combined canputer-connunication based education systems allowing real-time dynamic interaction among teacher, student, and machine have been proposed [10]. In such systems, a library of multimedia material would be organized for user control of a great variety of educational experiences.

One embryonic member of the multimedia family, the prcrecorded videocassette (or TV cartridge) is presently trying to establish its appropriate niche within these new educational schemes. The prerecorded videocassette serves as an "animated textbook", providing a dynamic display to enhance the learning rate of many subjects. Attention is directed in this paper to an analysis of this particular communication component.


At present, there appeal to be rour technically viable videocasaette systems: photographic film (both miniaturized [11] and Super-8 movie cartridge), magnetic tape, plastic video disc [12], and HoloTape [13,14]. Each of these systems

has certain advantages and disadvantages; however, in the long run, the two strongest contenders for the educational market will probably be magnetic tape and HoloTape.

Magnetic tape systems have benefited from decades of evolutionary development and they have now reached the point at which reasonably good pictures can be obtained from helical scan players in the $1,000 price range. Perhaps their most significant feature, as far as education is concerned, is that they offer record as well as playback capability. There is no doubt that magnetic tape is and will continue to be a very useful tool in educational systems.

For prerecorded programmed material, however, the advent of holography coupled with the development of lasers allows consideration of a new, low coat method for recording and playing back TV pictures. Compared to photographic film and plastic video disc systems, the HoloTape playback system is mechanistically simple and offers immunity to the deleterlous effects of scratches and dirt experienced with all systems under normal playing conditions.


The HoloTape player, illustrated in Fig.1, consists simply of a low power laser, a tape transport, and an inexpensive TV camera, the output of which goes to an ordinary TV receiver. The entire mechanism is enclosed in a small cabinet which prevents acceis to the laser.

As implied by its name, the HoloTape system uses a plastic tape on which images are stored in the form of embossed holograms, aa illustrated in Fig.2a, in operation, the plastic tape moves continuously through the laser beam, pro-







jecting a sequence of motion picture images (which fade from one frame to the next) into the TV camera. An example of the image of a "test pattern" is illustrated in Fig. 2b.

Advantages of the HoloTape system include:

Low Cost Cartridges - Relief phase holograms (see Fig.2a), which are essentially contour maps (see "hills" and "valleys" comprising surface detail of HoloTape surface in Fig.3) of interference patterns, can be emboased on low-cost, one-half inch wide plastic tape using a process limilar to that for replicating vinyl phonograph records. The final product la potentially 1/5 the cost of programmed magnetic tape.

Scratch and Dirt Resistance - The "redundant" nature [15] of certain holograms allows them to be scratched, spotted with dirt, and otherwise mutilated without significant loss of image quality. For comparison, the image from a "redundant" hologram is shown in Fig. 2b while the image from a "nonredundant" hologram is shown In Fig.4.

Image Immobilization - Fraunhofer holograms (a special configuration of the holographic recording technique described above) produce stationary images even though the holograms are continuously moving through the readout beam [16]. Thus, flicker-free images are reconstructed at any tape speed (including single frame stop motion) with no need for an intermittent-motion tape transport, moving shutters, or servo control between tape speed and TV scan rate.

Reliability - There are no high speed moving parts to wear out, and

Figure 3. Photomicrograph of the surface of one frame of a HoloTape (widths of ripples - 0.000001 meter).


Figure 4. Image from "nonredundant" hologram demonstrates image effect of dirt and scratches on tape illuminated with coherent (laser) light. Bulls-eye patterns are caused by dust specks while the "sauiggles" result from scratches.

optical alignment is not critical.

Disadvantages of the HoloTape system are: (1) sophisticated equipment must be used to record the tapes, precluding the possibility of the instructor recording his own HoloTapes (although he could record on magnetic tape or photographic film prior to having a HoloTape factory produce copies for mass dissemination), and (2) the system is still in an early stage of its evolutionary development cycle.

If we adopt an air of optimism and engage in some futuristic thinking about the potential of the HoloTape system, we can reach some interesting and perhaps very important conclusions. First, consider the cost of the plastic tape on which the TV programs are stored. Since raw material cost of a one-half hour TV program is approximately 25 cents and since many thousands of plastic tapes can be replicated from an original metal master, the manufacturing cost can be very low. Accordingly, embossed holographic tape is ideally suited for mass replication. Standard, well-proven courses prepared by an eminent scholar (such as University of California Professor Feynman's physics lectures) and short curriculum concept units (e.g.. Harmonic Phasors by W. H. Huggins and D. Weiner, NSF National Committee for Electrical Engineering Films, U.S.A.) fall Into the mass replication category.

The HoloTape system offers compatibility with all TV standards. Magnetic tapes, photographic film, and video discs must be recorded so as to match the TV standards of the system in which they are to be used. In contrast, holographic tapes can be played via any TV system by simply building the appropriate TV camera into the player of Fig.1. In this way, the same tapes can be played on a U.S.A. player, a French player, a Japanese player, a U.S.S.R. player, and so

on. Moreover, a sound recording method has been developed which requires very little tape width (about 0.01 inch) for the sound track, allowing bilingual sound tracks to be stored on the same tape. The national dialectal and international education benefits are obvious.


In September 1972, the College of Engineering and Applied Science of the University of Pennsylvania began operation of an instructional television system operating on frequencies around 2.5 GHz. In this system, the video portion of the telecast is one-way, but the audio portion is two-way, thus permitting students at remote receiving stations not only to see and hear the presentation in the classroom studio at the University, but also to participate in discussions and to, ask questions directly of the professor as he lectures This system, known as "Talk-Back Television", is one of eight such systems in the United States and is similar in operation (except for the.broadcast capability) to the closed-circuit television system at Leningrad Polytechnic Institute, which allows audio exchange between professor and students within a new building on the Institute grounds [4].

Figure 5 shows a schematic of the University of Pennsylvania system. The television classroom seats 38 students and provides a monitor for each set of two students. (A typical monitor is shown in Fig.6.) The professor faces the students and writes his notes on a pad (see Fig.8) which is viewed by an overhead television camera. This camera can scan the professor's desk top and thereby view artifacts which may be essential to a lecture. The overhead camera can also rotate and zoom in for closeup views of artifacts such as, for example, book pages, photographs, and electronic circuit components.



Fig. 5. Schematic of "Talkback Television System" at University of Pennsylvania. A photograph of the HoloTape player on the protester's desk is shown in Fig.7.



A second camera at the control room end of the classroom can view the professor and students.

Interaction with a computer is possible through a terminal at the professor's desk thereby allowing alpha-numeric and graphical data from the computer to be presented on all television screens. Note the location of the computer terminal in Fig. 5.

A rudimentary HoloTape cassette player is shown in the photograph of Fig.7. Tne identification of the player components is revealed by comparison with the schematic diagram of Fig.1. (Note the location of the HoloTape player on the professor's desk in the system drawing of Fig.5.)

As viewed on a television screen at a remote classroom, either in a dormitory or at a broadcast receiving site aa illustrated in Fig.5.


Video may eventually become the least expensive and most effective connnuni-cation medium for offering quality educational material. Video integrated with computer technology has the potential for creating an educational environment that will facilitate learning at times, rates, and locations most suitable to the individual student. The use of video in cassette form directly in the home or school, or through dial-up cable or broadcast service can evolve into a major system for general educational use including university degree programs; continuing education; education for the handicapped and home-bound; education for individuals at sites isolated from the larger community; and the exchange







of information among universities, government, and industry. As potentially the lowest-cost videocassette system, the HoloTape system may become an integral part of the educational technology systems of the future.


1. M. Meyerson and S.R.Graubard. "A First Report: The Assembly on University Goals and Governance," The American Academy of Arts and Sciences, January 1971.

2. The Carnegie Commission on Higher Education Special Report, "Leas Time, More Options: Education Beyond the High School," McGraw-Hill Book Company, New York, January 1971.

3. S. G. Tickton (editor). "To Improve Learning - An Evaluation of Instructional Technology," R. R. Bowker Company, New York and London, 1970.

4. J. W. Annsey and N. C. Dahl. "An Inquiry into the Uses of Instructional Technology," The Ford Foundation, New York, 1973.

5. R. E. Levien, et al. "The Emerging Technology - Instructional Uses of the Computer in Higher Education," A Carnegie Commission on Higher Education and Rand Corporation Study, McGraw-Hill Book Company, New York, 1972.

6. D. Alpert and D. L. Bitzer. "Advances in Computer-Based Education," Science, Volume 167, pages 1582-1590, 20 March 1970.

7. L. P. Grayson. "Computer-Assisted Instruction and Its Implications for University Education," Journal of Engineering Education, Volume 59, page 477, February 1969.

8. Commission on Education, "Educational Technology in Higher Education: The Promises and Limitations of ITV and CAI," A Report of the Instructional Technology Committee, National Academy of Engineering, September 1969.

9. Educational Product Report Number 31, "Instructional Television Fixed Service," Volume IV, Number 4, EPIE Institute, 386 Park Avenue, New York, 10016, January 1971.

10. J. Bordogna, D. K. Hsiao, and N. S. Prywes. "A General Purpose System for Computer-Communication Based Instruction," Proc. IFIP World Conference on Computer Education, Amsterdam, Netherlands, pages III/I-III/6, August 1970.

11. P. C. Goldmark. "Color EVR," IEEE Spectrum, pages 22-33, September 1970.

12. A Playback System created by G. Dickopp, H. J. Klemp, H. Redlich, and E. Schuller, Teldec, Inc. (a jointly owned company of A.E.G.-Telefunken and Decca Records, Ltd.).

13. R. A. Bartdlini, D. Karlsons, W. J. Hannan, and M. J. Lurie. "Embossed Hologram Motion Pictures for Television Playback," Applied Optics, Volume 9, October 1970.

14. W. J. Hannan. "Embossed Holographic Movies," Proceedings of the Fifth All-Union Symposium on the Physical Principles of Holography, Academic City, Novosibirsk, USSR, February 1973.

15. A. H. Fireater, E. C. Fox, T. Gayeski, W. J. Hannan, and M. Lurie. "Redundant Holograms," RCA Review, pages 131-153, March 1972.

16. R. A. Bartolini, J. Bordogna, and D. Karlsona. "Recording Considerations for RCA HoloTape," RCA Review, pagea 170-205, March 1972.

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