| 摘要 |
An improved method and apparatus for grey level printing using linear arrays of LED's or the like are described. In one embodiment, a circuit provides signals in serial form to an LED printhead having a binary architecture to print grey level pixels. The circuit includes a comparator that compares for each pixel to be printed a time-changing count from a threshold counter with a multibit signal representing a grey level value. If the grey level exceeds the count, a single bit signal is fed to the printhead and used to turn the LED on. This process is repeated to determine the "on" time of the LED for that pixel. In another embodiment, the number of repetitions of this process are shown to be substantially reducible by using a vernier clocking scheme involving a clock signal having different frequencies.
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