3. ELECTRONIC VISUAL COMMUNICATIONS:  HIGH-DEFINITION TELEVISION 
Electronic imaging, encompassing all aspects of imaging science, 
comprises capture, conversion, processing, storage and display. It already 
has had a profound effect in medicine, in noninvasive diagnostics; CAT 
scanners, ultrasonic imagers and digital radiography for example. It 
retains a high profile position as "machine vision." It is also on the 
threshold of altering the consumer video and photographic industries. This 
latter application is of interest to the photogrammetrist: how can these 
techniques complement, and even supplant, photobased ones? High definition 
digital TV and electronic still photography are waves of the future that 
will impact significantly upon photogrammetric practice, instrumentation and 
applications. 
Stereo photogrammetric instruments convey to the human observer pieces of 
the real 3-D world with static realism and metric fidelity, served well by 
high quality optics and chemical emulsions. Electronic imaging promises not 
only this function, but unlimited computer transformations, overlays with 
other images, graphics and text, data base merging creating new images from 
parts of the old, real-time geometric transformations and warping, false 
coloring and, perhaps most importantly, an instant window on a dynamic 3-D 
world. 
High definition (resolution) over a large format (typical of photographs) 
is where electronic imaging falls short. Although 4096x4096 monochrome 
electronic displays exist, there is currently no commercial area solid-state 
imager beyond the 640x600 pixel size, Wilson, 1985. (There is a 4000x4000 
pixel camera utilizing a CCD linear array with mechanical scanning, but its 
"frame rate" is 2 minutes.) Electronic image definition desired by human 
experience has been researched and indicates a lower bound around the 
1000x1000pixel size, Seeley, 1978, also supported by research and discus- 
sions on a new high definition television (HDTV) system for Japan, Fujio, 
1985. Interestingly, when it was decided to develop such a system it was 
for stereoscopic TV. Such a commercial based research effort can reduce the 
high cost of components, therefore the photogrammetrist can expect to 
benefit from this system development in a real way. In the years to come 
the 1000 line TV may no longer be a high priced venture having to employ 
electron beam cameras as input. 
It was recognized early, Schade, 1975, that the bandwidth-limited 
resolution of a TV image was something quite different from the grain 
limited resolution of a motion picture. As TV is originally an image system 
for conveying moving pictures, a balance must be maintained for the spatial 
and temporal characteristics of the human visual system. The frequency 
characteristic of the human visual system is shown in Fig. 1. 
Fig. 1 Response of the human visual 
system, (Fujio, 1985). 
  
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