Method and apparatus for grey level printing

Details Method and apparatus for grey level printing Method and apparatus for grey level printing

1989-12-18

1990-10-16

Miller, Jr., George H.

Facsimile and static presentation processing

Facsimile

Recording apparatus

346160, 358300, H04N 129, G01D 1514

Patent

active

049639897

ABSTRACT:
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.

REFERENCES:
patent: 4074319 (1978-02-01), Goldschmidt
patent: 4400738 (1983-08-01), Tomory
patent: 4443121 (1984-04-01), Arai
patent: 4455578 (1984-06-01), Fearnside
patent: 4525729 (1985-06-01), Agulnek
patent: 4750010 (1988-06-01), Ayers et al.
patent: 4819008 (1989-04-01), Nagato
patent: 4831395 (1989-05-01), Pham
patent: 4855760 (1989-08-01), Kanayama

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