Method and apparatus for parallel processing of a document image

#The present invention relates to document reproduction apparatus and methods and more particularly to apparatus and methods for processing of document image data for high productivity electronic copiers and printers.

#In the prior art of document reproduction apparatus, it is known to use non-impact recording apparatus that employ laser, light-emitting diode (LED), thermal, ink-jet or other recording sources for respectively recording images on an appropriate medium by forming picture elements or pixels. Data to be recorded may be derived from a computer, facsimile, or other source of electronic information or a document scanner that is part of an electronic copying apparatus. In the case of highly Productive reproduction apparatus, copies may be produced at over 100 copies per minute with very high image quality or resolution, say 600 dots per inch (dpi) (23.6 dots per mm). A typical production job may require multiple copies of a multipage document to be printed in collated order. As noted in U.S. Pat. No. 5,047,955, considerable time savings may ensue by rasterizing data for an image only once and printing the image plural times from a job image buffer (JIB) memory that stores the rasterized image in compressed form. Similarly, high productivity also results in printing multiple collated copies of a multi-page document without the need to rescan the image or to rerasterize electronic information.

#In commonly assigned U.S. application Ser. Nos. 07/982,365 and 07/982,546, there is disclosed a reproduction apparatus having two JIB processing paths. In a high productivity mode for processing single bit rasterized binary image data, rasterized data for the next document page to be stored in the JIB memory is stored in compressed form in the JIB memory having more available memory. For a page to be printed, the data for that page is extracted from the JIB memory, expanded and further processed to be sent to the printer in proper order. However, productivity for such an apparatus is limited by the data rates of the chips used to process the data downstream of the JIB memory.

#FIG. 1 is a schematic of a document reproduction apparatus of the prior art;

#FIG. 2 is a schematic of a portion of a document reproduction apparatus of the invention which may be used to increase the productivity of the apparatus of FIG. 1;

#FIG. 3 is a schematic of an LED printhead forming part of the apparatus of FIG. 2;

#The apparatus of the preferred embodiment will be described in accordance with an electrostatographic recording medium. The invention, however, is not limited to apparatus for creating images on such a medium, as other media such as photographic film etc. may also be used within the spirit of the invention, as well as other recording modes, i.e., ink jet, thermal, electrographic, etc.

#Because electrostatographic reproduction apparatus are well known, the present description will be directed in particular to elements forming part of or cooperating more directly with the present invention. Apparatus not specifically shown or described herein are selectable from those known in the prior art.

#With reference now to FIG. 1, an electrostatographic reproduction apparatus 10 includes a recording medium such as a photoconductive web if or other photosensitive medium that is trained about three transport rollers 12, 13 and 14, thereby forming an endless or continuous web. Roller 12 is coupled to a driver motor M in a conventional manner. Motor M is connected to a source of potential when a switch (not shown) is closed by a signal from a logic and control unit (LCU) 15. When the switch is closed, the roller 12 is driven by the motor M and moves the web 11 in a clockwise direction as indicated by arrow A. This movement causes successive image areas of web 11 to sequentially pass a series of electrophotographic work stations of the reproduction apparatus.