NON-IMPACT PRINT APPARATUS AND METHOD FOR GREY LEVEL RECORDING

摘要

A non-impact dot printer such as an LED printer, records grey levels of each dot by pulse width modulating the exposure on-time for each LED. The on-time of each LED for each exposure is controlled by comparing a count, representing an exposure time, with a second time changing count. The time changing count changes in accordance with clock periods of varying periodicity that are determined in accordance with human perception response criteria. This allows for the need for fewer data bits to define grey scale and exposure correction information reducing the number of data lines otherwise required. Clock periods are also changed in response to process conditions, i.e., the color of the image being recorded.