HOLOTAPE® SYSTEMS IN EDUCATION
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
In education, particularly higher education, there is an urgent
need for curricular innovation aimed at adapting teaching techniques to current
needs . 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 . 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
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
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 . 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.
THE POTENTIAL VIDEOCASSETTE SYSTEMS
At present, there appeal to be rour technically viable videocasaette
systems: photographic film (both miniaturized  and Super-8 movie cartridge),
magnetic tape, plastic video disc , and HoloTape [13,14]. Each of these
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 SYSTEM
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
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
Scratch and Dirt Resistance - The "redundant"
nature  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
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 . 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.
AN EXAMPLE HOLOTAPE EDUCATION SYSTEM
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 .
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.
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