How and when should I clean the lens?

• Clean the lens whenever you notice dirt or dust on the surface. To remove dirt or smears on the lens, use a commercially available cloth for cleaning glasses.
  
  Caution: Clean the lens gently to avoid changing the focus or misaligning the image with the screen. If this happens, see Adjusting the Image Position and Focus.
  
  Warning:
  Before you clean any part of the system, turn it off and unplug the power cord.