If the length of the minor axis of ellipse is equal to half of the distance between the foci, then the eccentricity of the ellipse is :

For an ellipse, the semi-minor axis is $$b$$ and the distance between foci is $$2c$$ where $$c = ae$$.

Length of minor axis = $$2b$$. Half the distance between foci = $$\frac{2c}{2} = c = ae$$.

Given: $$2b = ae$$, so $$b = \frac{ae}{2}$$.

Using the relation $$b^2 = a^2(1 - e^2)$$:

$$ \frac{a^2e^2}{4} = a^2(1 - e^2) $$

$$ \frac{e^2}{4} = 1 - e^2 $$

$$ e^2 + \frac{e^2}{4} = 1 \Rightarrow \frac{5e^2}{4} = 1 \Rightarrow e^2 = \frac{4}{5} $$

$$ e = \frac{2}{\sqrt{5}} $$

The answer is Option (4): $$\boxed{\frac{2}{\sqrt{5}}}$$.