Fator de Forma de Coddington

o

n

i

i

\frac{1}{f} = \frac{1}{o} + \frac{1}{i}

o

f

n

p

p = \frac{i + o}{i - o}

c

c = - 2 p \frac{n^{2} - 1}{n + 2} = \frac{r_{2} + r_{1}}{r_{2} - r_{1}}

r_{1}

r_{1} = 2 f \frac{n - 1}{q + 1}

r_{2}

r_{2} = 2 f \frac{n - 1}{q - 1}