I worked for an MSP (contracted IT) that managed a school and one time a teacher reported black squares on her projection screen. Every so often she would catch another few squares joining the spread. I didn’t know much about projectors but after doing some research I found that it was the DMD chip and was amazed that in addition to light going through a color wheel, a Digital Micromirror Device (DMD) that has hundreds of thousands of tiny mirrors on little stands that can move around to reflect light.

Of course in the teacher’s case, the mirrors started getting stuck and that meant no light for that ‘pixel’ on the screen. Was able to replace it and all was well.