Abstract: An image reading apparatus includes a plural number of line image sensors disposed on a read line, a background detection circuit for detecting a background level of an original document on the basis of an image signal from a sample portion of a reference line image sensor as a line image sensor facing the original document. The sample portion is predetermined as a portion facing the original document. The apparatus also includes a conversion circuit for converting image signals output from the line image sensors, into image data expressed as a relative level when the background level detected by the background detection circuit is used as a white reference level.

Abstract: A digital copier having a single scanner and a plurality of plotters which are physically independent of each other. The plotters may be designated one at a time. When the designated plotter is already operating, another plotter which is idle is designated. When all the plotters are in operation at the time of designation, image data representative of a document read by the scanner are stored and, as soon as a designated plotter becomes idle, the plotter begins to plot the stored image data automatically. Further, when an error occurs in any of the plotters being operated, the copying operations are handed over to another plotter.

Abstract: The surface of an electrostatic drum (12) is charged and radiated with a light image of an original document (16) to form an electrostatic image which is developed to form a toner image. A copy sheet (18) is moved into engagement with the drum (12) and an electrostatic charge applied thereto to transfer the toner image to the copy sheet (18). A corona discharge unit (27) applies an alternating voltage to the leading edge of the copy sheet (18) to discharge the same and cause the leading edge to separate from the drum (12). Thereafter, the discharge unit (27) applies an asymmetrical alternating voltage which partially discharges the remaining portion of the copy sheet (18) but does not cause the same to separate from the drum (12).

Abstract: The apparatus comprises a projection optical system and a copying system. The projection optical system can project an image of an original either onto a screen or to an exposing position of the copying system by switching between two positions. The copying system comprises a plurality of chargers providing different charging conditions in accordance with the types and sizes of copy sheets, by utilizing a change-over switch. A plurality of switches adapted for use with copy sheets of different lengths are arranged along the path of movement of a sheet of paper and, when the switch corresponding to the particular length of copy sheet desired is actuated, the movement of the sheet of paper is stopped, so that the central portion of the copy sheet can be brought into alignment with the optical axis for exposing at all times regardless of the difference in the length of copy sheets.