Your optical block (projector) is beginning to go bad. This is a very common issue, for which Sony offered a limited warranty extension.
Your first step is to contact Sony at (888) 649-7669 to verify warranty status. If they say it's too old, check to see if you have an extended warranty plan. This issue will progressively get worse. If you get no relief from either, watch it until it craps out and save up for a new set.