How is the image focused and not a big blur?
replies(2):
All light in a narrow cone extending from the camera gets recorded to one pixel, entirely independently from other pixels. There's no reason this would be blurry. Blur is an artifact created by lenses when multiple pixels interact.
There is a lens in the apparatus, which is used to project the image from the mirror onto the pinhole, but it is configured so the plane of the laser is in focus at the pinhole.
What I don't understand is how the projection remains in focus as the mirror sweeps to the side, but perhaps the change in focus is so small.