Circuit enhances vertical resolution in electron beam, raster scanning systems exhibiting aperture distortion in the vertical direction. A sensitized area /image/ produces a video output when the scan beam nears it, which causes vertical elongation in the reconstructed images of all sensitized areas on the surface

Alsovsky, W. H.

Greenwood, J. R.

Holley, O. M.

English

NASA Technical Reports Server

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April - 1968	 Brief 68-l0121 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Circuit Enhances Vertical Resolution in Raster Scanning Systems 
Video In
The circuit represented by the block diagram is 
designed to enhance vertical resolution in electron 
beam, raster scanning systems exhibiting aperture 
distortion in the vertical direction. A sensitized area 
(image) whose boundary lies more than one sweep-
width away from the scan beam position produces 
a video output when the scan beam nears it. This 
effect produces vertical elongation in the recon-
structed images of all sensitized areas on the surface
as well as smearing between vertically adjacent, closely 
spaced images. 
The method used to compensate for the distortion 
and its attendant loss of resolution is based on a real-
time comparison between the vertical characteristics 
of an image and its immediate future and past history. 
In the television raster system, video signals are 
delayed by exactly the horizontal scan period. Two 
such delay increments are used so that three corn-
(continued ovcrleaf) 
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plete (two delayed and one real-time) video lines are 
available simultaneously and are in horizontal syn-
chronization. As indicated on the block diagram, the 
incoming video signals are delayed one horizontal 
period each by the delay lines. The resulting signals 
are X (undelayed), Y (delayed one period), and Z 
(delayed two periods). These signals are processed 
by sequential addition, inversion, and attenuation 
(attenuator constant typically less than 0.5) so that 
the video output becomes: Y + K [Y —(X + Z)1. 
Resolution enhancement is attained through contrast 
enhancement between closely vertically spaced images. 
This enhancement is achieved at the expense of some 
loss in contrast of vertically continuous images. 
Notes: 
I. In its present stage of development, the circuit is 
not suitable for vector/alphanumeric displays, be-
cause these require higher horizontal resolution 
than is now practicable with the circuit.
The basic concept of this circuit may be applied as 
a means of enhancing the signal-to-noise ratio as 
well as vertical resolution in raster scanning 
systems. 
3. Technical details may be obtained from: 
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058 
Reference: B68-10121 
Patent status: 
No patent action is contemplated by NASA. 
Source: J. R. Greenwood, W. H. Alsovsky, 
and 0. M. Holley 
of Philco-Ford Corporation 
under contract to 
Manned Spacecraft Center 
(MSC-12123) 
N1)LIV	 WJV 
.11 OS)1	 9LL	 U
ds 
Brief 68-10121	 Category 01


Circuit enhances vertical resolution in raster scanning systems

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