v Spread through a number of years. 
     
  
  
   
   
   
   
   
   
   
   
   
   
   
   
   
    
   
   
   
    
    
    
    
    
   
    
transformation functions relating the tilted photo to the horizontal plane, 
producing the necessary change in the scan angle for each scanned line, In 
this manner rectification perpendicular to the principal line of tilted neg= 
ative is achieved, 
An electric analog computer shown as computer #2 in Fig #L solves the 
transformation equations for rectification along the principal line of the 
aerial negative. This computer coupled with the motion of the transparent 
copy table, determines the rate at which the ULM, mounted on the recording 
carriage, advances along the recording cylinder. The rate of travel of 
the recording carriage increases as the rate of change in scale from one 
scan line to the next increases, 
The aperature of the ULM becomes larger (parallel to the axis of rota- 
tion of the recording cylinder) as the traanparent copy table advances out- 
ward along the principal line of the negative, In the direction of the 
recording (perpendicular to the rotation axis of the recording cylinder) 
the aperature remains constant for uniform exposures. 
A relative measure of the resolution characteristics of a tailed 
photograph is illustrated in Fig #lie The resolution characteristics of a 
rectified photo, should be representative of the same characteristic curvee 
From Fig #lı a tilted protograph containing 0° y tilt, the resolution above 
the isoline will be better in a direction parallel to the x axis and below 
the isoline the resolution will be better perpendicular ho the x AX13e 
The Electronic Rectifier as designed preserves the same relative reso 
lution characteristics inherent in the original photograph. This does not, 
however, mean the present instrument is capable of reproducing better tahn 
5