Image reader with variable magnification dependent on desired dot density

Claim 1

An image reader for reading indicia on a document comprising: means for optically projecting an image of said indicia on said document; optical magnification variation means for varying a real magnification to vary a size of the optically projected image; an image reading device for transforming the optically projected image into electrical signals, said image reading device including a plurality of reading elements and having a predetermined reading element density; means for transforming said electrical signals output from said image reading device into bi-level signals; means for designating a picture element density, said picture element density corresponding to a designated number of reading elements per a unit dimension of indicia; means for designating a resultant magnification; means for controlling said optical magnification variation means to set the real magnification to project the unit dimension of indicia onto a particular number of reading element, said particular number determined in accordance with said designated picture element density and said designated resultant magnification.