\begin{figure}[htbp]

\centering\subfigure[]{\includegraphics[width=0.6cm]{fig02a}}

\centering\subfigure[]{\includegraphics[width=1.6cm]{fig02b}}

\centering\subfigure[]{\includegraphics[width=2.2cm]{fig02c}}

\centering\subfigure[]{\includegraphics[width=3.2cm]{fig02d}}

\end{figure}

이렇게 한상태입니다.