point-or slit- images on the emulsion (scan photography or strip - and 
panoramic photography) the real time advantages of imaging are lost, 
since the photgraph is then created by moving the shutter opening relative 
to the emulsion over a finite time interval while the sensor platform is 
moved. Contrary to frame camera images scan,-strip-,or panoramic photo- 
graphy has therefore additional dynamic distortions due to irregularities 
in platform-attitude or platform-motion and in film or shutter movement. 
If photographic emulsions cannot be used, imaging must occur in an 
indirect manner. 
In the visible, or near visible light range one may utilize optical pro- 
jection to create a two-dimensional image on the surface of a vidicon- 
or orthicon-imaging tube. The phosphor particles store the projected real- 
time image for a limited time period. They too are only sensitive within 
the range fromA=0.3 to 1.0 um and must be scanned electronically to ob- 
tain a time varying sequence of point by point image densities. From 
these the indirect image may be reconstructed on a television tube and 
photographed onto a photographic emulsion for permanent two-dimensional 
storage. Since electonic scanning occurs in real-time dynamic distortions 
do not occur, however additional distortions through inaccuracies of the 
tube components used for electronic scanning are present. 
Outside the limits of the visible or near visible light range it becomes 
difficult or impossible to generate a two-dimensional array of energy 
sensitive particles to which the energy may be directed. Instead one 
quantum detector may be used to generate a time varying sequence of re- 
ceived radiation signals. The direction of the signals is controlled by 
mechanical scanning. 
  
In the infrared and ultraviolet ranges scanning is achieved by prisms 
which rotate in a direction perpendicular to the forward movement of the 
scanner platform} Thus the radiation of a continuous sequence of image 
* Only A.G.A. produces a mechanical scanner operating in two dimensions in 
real time. The image is restricted to a narrow image angle (5x59,extendable 
to 25x259) and a low resolution (5mrad).The display is made through a tele- 
vision system. 3