strehl - computer some parameter (include Strehl ratio) of the field
the strehl ratio is calulate by below expression:
besides Strehl(the first value of out), other five parameters of the field are computed. they are: the total energy; the center of gravity in x and y direction; Standard deviation in x, y,and r direction.
f0=begin(0.01,1e-6); f1=circ_ap(f0,0.005); f2=forvard(f1,1); [str,f3]=strehl(f2); field_plot(f3); str(1)
Chen jingyuan, Gan guangyong (IAPCM, Beijing,China.)