Clean the projector’s obstacle sensor glass (circled in red) periodically, or if you see a message telling you to remove any obstacles that are interfering with the projection area.
To remove dust or smudges, gently wipe the obstacle sensor glass with lens-cleaning paper.
To remove stubborn smudges, moisten a soft, lint-free cloth with lens cleaner and gently wipe the obstacle sensor glass.Warning: Do not use a lens cleaner that contains flammable gas. The high heat generated by the projector lamp may cause a fire.
Do not use canned air, or the gases may leave a flammable residue.
I have worked in the computer repair field since the early '90s. I was a technician and then Coordinator of Computer Repair for Regional Education Service Agency II (RESA 2) for 18 years. I currently work for Wayne County Schools as a Network Engineer/Technology Specialist. I am responsible for the schools' Internet access, Wi-Fi, networks, servers, laptops, desktops, and operating systems and software.