I answer this question like ten times a day so don't feel bad.
The blu-ray laser in your PS3 is a three part laser (cd / dvd / blu-ray). They last only 1-3 years with average use. It's a Sony defect.
Check out my common PS3 problem and repair guide for tips and suggestions for your problem.http://rescuetechla.blogspot.com/
Please feel free to email me any other questions and please don't forget to rate!