18 
  
  
  
  
  
  
  
  
  
Fig. 3. Consequences of the transformation of the origin of the image coordinate systems 
from the prineipal points (H’ and H”) to the isocenters W’ and W” respectively. 
y 
(æ"); = — ctan A (40) 
, 04 
(y); — ctan 7 (41) 
” Ÿ 2 € 
(x"); = — ctan "d (42) 
My 
(y"); — ctan — (43) 
c is the calibrated focal length. The signs depend upon the definitions 
of the rotations ¢ and w. See fig. 8. 
The coordinates (x’) (y’) and (x")(y") can be transformed into the 
coordinates x'j' and x” y” respectively by two translations and one 
rotation. The translations are identical with the expressions (40)—(43) 
above. The rotation dx can, according to fig. 3, be determined from 
the expression 
Wo 04 
ctan —, — ctan 
- - 
dx == — —— (44) 
; Pa P1 
b' — clan — + ctan -