Digital copier having switchable pixel densities

Claim 1

A digital copier capable of printing out image data which are outputted by another machine connected to said copier, comprising: a reading section for optically reading a document to be copied and outputting the read document in the form of first image data; an inputting section for receiving and outputting second image data which are fed from said another machine; a writing section for writing a series of images of one of said first and said second image data, sad writing section comprising a light source, illuminating optics for causing light to substantially converge on an optical axis of said light source, a rotatable polygonal mirror located downstream of an optical path of said illuminating optics, reflecting optics for converging in the form of a beam spot the light which is reflected by said polygonal mirror for scanning, and an imaging surface on which said light spot is scanned relative to said imaging surface and focused in the form of a pixel; and switching means installed in said writing section, responsive to one of said first and second image data, for switching a pixel density for a series of images to one of a plurality of pixel densities selected so that said selected reading section first image data and said inputting section second image data, wherein said illuminating optics comprises a plurality of lenses each having a different focal length, said switching means being constructed to select one of said lenses, and wherein said switching means comprises holder means loaded with at least two of said lenses which are individually positioned on independent optical axes which extend along said optical axis of said illuminating optics, said lenses being individually adjustable in position on said holder means, holder driving means for driving said holder means in a direction perpendicular to said optical axis, and positioning means for selectively stopping said holder means at a predetermined position where an optical axis of one of said two lenses coincides with said optical axis of said illuminating optics and a predetermined position where an optical axis of the other lens coincides with said optical axis.