scanneur à ouverture hélicoïdale rotative

OBS: The helical aperture facsimile transmitter is fairly common on low-to mid-volume fax units. The original is roller fed over a flatbed copy platen and illuminated by an area lamp. Lens and mirror optics reflect and focus one scan line of the moving document at a time, first through a fixed horizontal slit aperture, and then through a rotating helical aperture. The rotating of the helical aperture produces one lateral scan of the original per revolution, with the passing light being focused a final time onto a photocell for conversion to an electrical signal.