Method and apparatus for grey level printing

摘要

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.