解：由題意得??$∠AOC=∠BOD.$??
∵??$B'$??與??$B$??點(diǎn)關(guān)于鏡面??$CD$??對稱，
∴??$OB'=OB$??，??$DB'=DB=4\ \mathrm {m}$??，??$∠BOD=∠B'OD.$??
∴??∠$AOC=∠B'OD$??，即??$A$??，??$O$??，??$B'$??三點(diǎn)共線??$.$??
∴入射光從點(diǎn)??$A$??到點(diǎn)??$B$??經(jīng)過的路程為??$OA+OB=OA+OB'=AB'.$??
∵四邊形??$ACDB$??是矩形，
∴??$∠ABB'=90°.$??
∴??$AB'=\sqrt {AB^2+BB'^2}=\sqrt {6^2+(4+4)^2}=10(\mathrm {m}).$??
故入射光從點(diǎn)??$A$??到點(diǎn)??$B$??經(jīng)過的路程為??$10\ \mathrm {m}.$??
