A check of the computations can be made at this point by defining the 

 quantities, L'', as below. The sunn of the 861 values of L* thus obtained 

 should equal Q(0, 0). Thus 

 L*(r, s) = L(r, s) 



for r » 1, , , . , , 19, s = -19 to + 19 



and 



L*(0,s) =-Jl(0,s) s = -19 to +19 



L*(20,s)=-|l(20, «) s = -19 to +19 



L*(r, 20)=-iL(r,20) r = 1 to 19 



L*(r,-20)=4L(r,-20) r = 1 to 19 



and 



L*(0, 20) = ]-L(Gu20) 



L*(0,-20) =1l(0,-20) 



L*(20.20) =|l(20,20) 



L*(20,-20) = ^L(20.-20). 



Also, in order to smootk on the line r = and on the edges, the 



values of L, are continued by the following equations. 



L(-l, b) = L{1, -b) a = 0, 1, , +20 



L(a, 21) = L(a. 19) b = -20, -19, . . . . , 0, , +20 . 



L(a,-21) = L(a,-19) 



L(21.b) = L(19.b) 



L(-21,-21) = L(-19.-19) 



L(21,21) = L(19,I9) 



The smoothing filter ia ft Utraightforward extension of the smoothing 



69 



