Could be a bit of dust or fuzz inside of the lens element or by the DLP is a very common "dusty" environment, then you may have some cleaning to do. Be careful not to try and blow out the more...
except the lamp. Contact your dealer if other parts needs replacing. Cleaning the Lens Clean the lens whenever you notice dirt or dust on the surface. Use a canister of compressed air to remove more...
BenQ PB6210 Multimedia Projector - User Guide (page #37)