A THEORY OF SCANNING 



471 



phase angles of the cosine components, or the complex amplitudes of 

 the exponential components, remain constant with time. For a mov- 

 ing subject these complex amplitudes may be considered modulated as 

 functions of time. 



-3 COMPONENT 



+ 2, -1-3 COMPONENT 



0, +2 COMPONENT +2,0 COMPONENT 



Fig. 3 — Examples of field components. 



The real amplitudes amn for a circular area of uniform brightness on a 

 black background are relatively easily calculated, and this subject is 

 also a good one to study as a picture from some points of view because it 

 has a simple sharp border sloping in various directions. The amplitudes 



