The ps3 can read blu-ray movie files directly. They are in the form of .m2ts(High Definition format)
edit: it seems people are having issues playing .m2ts directly on the ps3 (has to do with audio not being ac3)
you can try converting to avchd structure
attached is link to a multiavchd
" watch Blu-ray Disc backups without reencoding (PS3) (just select your movie M2TS file
from the original BDMV\STREAM folder (the largest one) and use it with multiAVCHD (or import the whole BDMV folder in RE-AUTHOR mode);
multiAVCHD will split it in 4GB chunks, so you'll be able to transfer it to your external USB disk or USB flash drive. "
http://multiavchd.deanbg.com/