Best bet is to send it off to a console repair shop (NOT SONY)
If you dont want to spend the money on that though then i can suggest a new bluray drive, you can get them on ebay from £40-£65, I bet you paid £30 for the lens right? should have spent the extra 10-20 :P
But remember you have to put the logic board on your current bluray and put it onto the new one you have purchased as it is linked with your motherboard.
If that fails then it is most likely your bluray logic board and you would need a new one of them.
Getting a new logic board is a pain because you have to link it your motherboard again, which isnt easy. So if its your logic board your best bet is to buy a brand new motherboard (refurbished) from ps3spares.com, they give you the linked logic board with the motherboard so you dont have to remarry it.
Buying a new ps3 would be easier but if your up for that little challange then go ahead :P
Oh and btw, remember to buy arctic silver thermal paste for the cpu & gpu if your going for the motherboard option, wouldnt want that new mobo to overheat xD