Patent ID: 6434347
Filing Date: 2002-08-13
Classification: G03G

Abstract:
A printing apparatus comprising:a belt unit which conveys record sheets on a belt at a constant speed, said record sheets being electrostatically adhered to a surface of said belt; a plurality of electrostatic recording units arranged in a direction of conveyance of said record sheets, said electrostatic recording units forming a latent image corresponding to image data through an optical scanning on a photosensitive drum in rotation by an exposure device, said electrostatic recording units developing said latent image with a toner component of different color, to thereafter transfer said developed image onto said record sheets lying on the surface of said belt; a toner transfer unit which transfers a halftone pattern onto the surface of said belt by use of said plurality of electrostatic recording units; a sensor unit which optically reads said halftone pattern transferred onto the surface of said belt; and a toner density measurement unit which measures a toner density on the basis of a ratio of a reflected light from a toner bearing portion to a reflected light from a toner free portion in a read signal of said halftone pattern from said sensor unit.