If you have a dead or non working Blu-ray drive here is a tutorial to help you replace your Blu-ray drives lens youself from another working Blu-ray drive or just purchasing the entire part needed (kem-400aaa).
Please note that if you have warranty or a store receipt return/call Sony and they should be able to do it for free. But if your out of warranty or dont have any on your PS3 (for any devilsh reason), you can easily fix your PS3. (Sony charges about $150 to do it).
1) Open the top cover of the PS3.
2) Pull out the power plug for the Blu-ray drive.
3) Carefully pull up the Blu-ray drive and unclip the data cable ribbon from PS3 drive.
4) Remove the two silver screws on top right and bottom right according to the picture (screwdriver is pointing at them)
5) Unsrew the 3 black screws to the left as well (screwdriver pointing)
6) Remove the top metal sheilding of the Blu-ray drive, exposing the guts.
7) Remove the top frame now that we are inside to reveal the laser (unscrew the screws)
8) Once that is done you should be staring at the Blu-ray laser.
9) Remove the Blu-ray lens screws
10) More screws to remove (screwdriver pointing)
11) There you go after removing all those screws the laser should easily come out, simply repeat the process for another working Blu-ray drive and extract its Blu-ray lens or just simply buy a replacement part (part #kem-400aaa) and insert it in the Blu-ray drive and start rescrewing.
Hope this can help those unfortuante with a dead bluray drive and no warranty.