ini" 
>. 
- 
> 
~, 
T —— D 
= 
^, 
  
  
M 
  
  
  
  
  
  
  
  
Inege 'SQURSH' due to - 
DECREASED SCAN SPEED, STANDARD VELOCITY 
or STANDARD SCAN SPEED, INCREASED VELOCITY 
Figure 8 
2.1.3 Creating Relative Motion 
  
The method of creating relative movement between 
the line-scan camera and the object of interest 
has so far been considered to be lateral motion, 
parallel to the camera baseline. This does not 
have to be the case. Instead, the type of movement 
can be altered to suit a given application where 
lateral displacement may not be appropriate, ie: 
internal pipe inspection. To produce suitable 
images it is only required that correlation exists 
between the method of displaying the information 
and the technique used to obtain the picture 
information in the first instance. With this in 
mind, another obvious method of creating the 
required movement is by rotation of the line-scan 
camera in front of the stationary object of interest 
(or vice versa). 
2.1.4 Rotational Movement 
  
The field of view produced by the relative motion 
of the line-scan camera with respect to the object 
is determined by the interaction of the scan rate 
and the translation/rotation speed. This has 
already been discussed with respect to lateral 
movement in Section 2.1.2. If this aspect of the 
line-scan arrangement is now applied to rotational 
displacement the following points will apply:— 
       
   
    
  
   
   
    
  
  
  
  
  
  
  
    
   
   
    
   
    
    
   
    
   
    
   
     
   
    
  
    
a. the field of view (and thus the 
resolution) of an image can be varied 
from any arc up to 360 degrees (Fig. 
9); 
b. if the field of view is less than 360 
degrees, the area of the object space 
under consideration will depend on the 
start point of image capture (Fig. 10). 
     
FIELD OF VIEW \ 
V 
Figure 9 Variable Field of View 
Taking each of these points in turn. If a 360 
degree field of view is set up, the images 
produced will contain information from an area of 
the object space completely surrounding the 
line-scan camera. This field of view can then be 
subsequently adjusted to cover a smaller arc and 
this used interactively with the image start point. 
The resultant images can then display information 
at a given resolution from any part of the observed 
object space surrounding the camera. 
s 
- - 
>>’ 
  
Figure 10 Variable Image Start Point 
It is important to realise that the images produced 
using rotational movement between the line-scan 
cameras and the object of interest can be difficult