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INTRODUCTION
J. W. GEBHARD, The John Hopkins University Applied Physics Laboratory
Despite the mutterings occasionally heard about how automatic signal
detection and evaluation devices are putting the eye out of business, one observes
little diminution in the use of visual displays of all kinds in current and projected
military and civilian control systems. The instrumentation of aircraft cockpits,
combat information centers, ground surveillance systems, arid air traffic con-
trol towers is still being designed about the human eye. Indeed, as long as the
brain of man retains its adaptability, and the sensitivity of the eye is about 6 db
above that of the theoretically perfect detector, there appears to be an assured
role for the visual display. ~
(
One of the most versatile kinds of display is the cathode-ray tube, which has
proved so important in radar and sonar work. It was just ten years ago that
Soller, Starr, and Valley, of the Massachusetts Institute of Technology Radiation
Laboratory, so admirably described the research and development work on
cathode-ray-tube displays that came out of World War II.1 Two years later
Lawson and Uhlenbeck, in another volume of the MIT series, offered a systematic
treatment of the detection of threshold signals.) Soon afterward, the large amount
of human factors work on radar scopes that had accumulated was published
without critical comment by Baker and Thornton.3 This useful compendium,
unfortunately, is classified, although it largely contains data that are now un-
classified. While many of the old difficulties remain with us, the operational
requirements of most systems have changed with the world, and display prob-
lems are not quite the same today as they were ten years ago. The time has
come to determine once again what is required of radar and sonar displays, and
how visual needs in particular are being met by the technical developments of
recent years. It is most fitting that the Committee on Vision should undertake
to do this, arid the Symposium on the Illumination and Visibility of Radar and
Sonar Displays, reported herein, is a welcome start in this direction.
The Symposium was open, which was doubtless the proper way to begin.
It is to be expected, however, that some of the more important research and
development in visual displays will have applications to national defense and,
therefore, will be classified. A complete appraisal must consider this work also,
and it is hoped that the Vision Committee will not limit its interest to the open
material.
Present surveillance systems utilizing cathode-ray-tube displays have
changed more by making familiar requirements harder to meet than by intro
iSoller, T., Starr, M. A., and Valley, G. E. Cathode-ray-tube displays. Massachusetts Institute
of Technology, Radiation Laboratory Series, Volume 22. McGraw-Hill, 1948.
~Lawson, J. L. and Uhlenbeck, G. E. Threshold signals. Massachusetts Institute of Technology,
Radiation Laboratory Series, Volume 24. McGraw-Hill, 1950.
3Baker, C. PI. and Thornton, G. B. Guide to factors affecting radar operators' efficiency.
Defence Research Board, Department of National Defence, Canada, 1953, DMRL Report No. 84.
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ducing new ones. For examples the necessity for surveying much larger blocks
of space than was once the case is the perennial range problem. We need also to
find increasingly smaller objects in the presence of increasingly greater noise.
Noise has always been on our cathode-ray tubes in a self-generated form. The
art of countermeasures now makes noise a weapon against the display itself.
No one has ever complained of having too much time in which to use a display,
yet the time to detect and identify signals continues to shrink. The inevitable
result of such considerations has been the development of much new equip-
ment, from new radars and sonars to new display methods. No attempt can be
made here to trace the many ramifications of this complex field. The most that
can be done is to mention some of the display problems that relate most closely
to the science of vision.
The first problem is the visibility of threshold signals on cathode-ray tubes.
This is much-plowed ground, but the old work does not help us greatly in pre-
dicting the visual efficiency of new tubes and new phosphors, or in knowing
what to expect of new developments in the presence of noise due to electronic
jamming. The advent of storage tubes imposes the requirement that we learn
how to assess and use these rather unconventional displays. The development
of automatic signal detection systems challenges the superiority of the eye where
it has always been supreme- in sensitivity. Under what conditions is the eye
better than the machine? Are there target-enhancement schemes in which the
eye can play a part?
A second problem is the identification of signals. Here the eye is confronted
by the ear as well as the machine. The possibilities contained in the aural identi-
fication of radar signals have been explored by Licklider4 with generally fa,ror-
able results, and the machine may be expected to perform a spectrographic
analysis on the signal. Can the information contained in electrical signals also be
presented for visual identification with any hope of success? Which of these
systems can operate best in the noisy environment?
A third problem concerns the use of displays for functions other than detec-
tion and identification, for example, controlling and decision making. Ten years
ago the inputs to visual displays came directly from the radar and sonar receivers.
Familiar control functions such as tracking are still of interest, but we now
frequently see secondary displays of data that are generated by computing sys-
tems. These new displays have properties and uses that are quite different from
conventional presentations. They are intense; noise is usually not a problem;
they may be generated continuously; all sorts of symbols may be written on
them; signals may be enhanced, suppressed, coded; and a flick of the switch
can change their inputs. Some of the perceptual problems encountered in such
displays are anticipated in the Vision Committee's Symposium on Form Dis
4Licklider, J. C. R. Studies in aural presentation of information. Operational A pplications
Laboratory, Air Force Cambridge Research Center, Air Research and Development Command,
Tech. Report No. AFCRC-58-53, 1957.
-2-
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crimination, but too little is known of the other visual requirements for the
design and use of these special-purpose displays.
:Finally, there is the problem of using cathode-ray tubes in environments
where the visual requirements imposed by the scopes are at variance with those
of other visual tasks. Much has been accomplished by the specialized lighting of
work places, and by the development of tube types that may be used in daylight.
Nevertheless7 the difficult job of reconciling incompatible demands on vision has
been handled largely on an ad hoc basis that has produced few general principles.
Perhaps this kind of solution to a particular lighting problem is the only one,
vet it would seem that a more generalized method, such as Blackwell suggests
for interior lighting, might be used here too.
The challenge afforded by a complete technical analysis of the visual re-
quirements of visual displays is big perhaps dismayingly so if one remembers
that the cathode-ray tube is only one of the many types of visual display. Never-
theless, the reward will equal the challenge since the eye still remains the most
important avenue of getting complex information into the observer's brain.
-
5Wulfeck, J. W. ancl Taylor, J. H., (Eds.) Form discriminatic~n as related to military problems.
Armed Forces-NRC Committee on Vision, National Academy of Sciences-National Research
Council, 1957, Pub. No. 561.
Representative terms from entire chapter:
radiation laboratory
