\begin{table}%t1
\caption{\label{table1}Summary of theoretical values and laboratory measurements of the pixelation noise properties.}
%\centering
\small
\begin{tabular}{ccc|cc|cc}
\hline \hline 
Prototype & $S$ & $p$ [$\mu$m] & \multicolumn{2}{c|}{$f_g$ [$\lambda/D$]} & \multicolumn{2}{c}{$I_g$} \\
& & &   theory  & experiment   &  theory & experiment \\
\hline
mask 2 & 200 & 15& 108   & $107$   & $5.7\times10^{-6}$ & $6.2\times10^{-6}$ \\
mask 3 & 100 & 30 & 54   & $53$ &$2.3\times10^{-5}$ & $3.3\times10^{-5}$\\
mask 4 & 50 &  60 & 27   & 25  & $9.1\times10^{-5}$ & $9.9\times10^{-5}$\\
mask 5 & 25 & 120 & 13  & 13 & $3.6\times10^{-4}$&  $3.5\times10^{-4}$\\
mask 6 & 12.5 & 240& 7  & 7 &$1.4\times10^{-3}$& $1.1\times10^{-3}$ \\
\hline
\end{tabular}
\end{table}