Abstract: A method and apparatus for grey level printing includes a plurality of recording elements which are enabled for variable periods of time during a cycle of recording grey level pixels. For each recording element a comparator compares the count in a time-changing exposure counter with a multibit grey level data signal. The exposure counter is decremented/incremented by exposure clock pulses from a programmable exposure clock. The exposure clock includes a master clock and an address counter that provides an incremented address signal in response to each set of N pulses from the master clock. The address signal identifies a location in memory of a set of signals used to generate exposure clock pulses. The set of signals is output in parallel to a serial shift register and shifted out serially to form the exposure clock pulses for decrementing/incrementing the exposure counter.

Abstract: A method and apparatus for resequencing image data for a non-impact printer having a plurality of recording elements. A memory stores image data such that image data for plural recording elements are stored at one address location. The memory is sequentially addressed so that the data stored at successive addresses are sequentially output from the memory in a sequence suited for the type of printhead. A multiplexer controls the outputs from the memory so that only data in the correct sequence is output at each address location during a first empty cycle whereas other image data at each address location are output at subsequent empty cycles.

Abstract: Method and apparatus for generating a process control patch on a charge-retaining member in a photocopier or printer. Patch data is stored in binary form for a small portion of the first two lines of the patch. This data is replicated throughout the patch to provide the pixel data for the entire patch. Blank pixel data is sent to the printhead during portions of line scans which do not contain the control patch.