\begin{table}%t1
%\centering
\par
\caption{Main properties of the PIAA configuration and 3 CPA configurations. IWD stands for Inner Working Distance, and is the smallest angular distance at which a~$10^9$ contrast is reached in the PSF. The Discovery space is the fraction of the field of view usable for faint companion detection.\label{tab1}}
\begin{tabular}{cccc}
\hline\hline
 & Transmission & IWD & Discovery Space \\
\hline
PIAA & 1.00 & $\approx$$ 1.5 \lambda/d$ & 1.00 \\
Jacquinot & 0.285 & $\approx$$ 5 \lambda/d$ & $\approx$$ 0.25$\\
Spergel & 0.273 & $\approx $$4 \lambda/d$ & $\approx$$ 0.5$ \\
ASA & 0.107 & $\approx $$4 \lambda/d$ & $\approx$$ 0.5$\\
 & & & (increases \\
 & & & with distance)\\
\hline
\end{tabular}
\end{table}