MULTI-FORMAT LASER PRINTER EMBODYING A METHOD FOR CHANGING OUTPUT IMAGE SIZES

摘要

The laser printer uses a rotating polygon (30) and a cylindrical mirror (44) disposed between the polygon and an image zone. The cylindrical mirror corrects for pyramidal errors in an output image formed on a moving photosensitive member (PM) disposed at the image zone by making the operative polygon facet and the image zone optionally conjugate in the page scan direction. To change the length (S1, S2) of the image in the line scan direction at the image zone, the optical distance between the polygon and image zone is varied by moving the cylindrical mirror. The velocity of the photosensitive member is adjusted to change the length of the output image in the page scan direction. At the new image format size, the cylindrical mirror makes the operative polygon facet optically conjugate with the image zone in the page scan direction to correct for pyramidal errors.