A CDE Definition
The unit within a printer that does the actual printing. In a laser printer, it includes the laser and mechanism to transfer the toner onto the paper. A printer engine is specified by its resolution and speed. See electrophotographic.
The printing technique used in laser and LED printers and most copy machines. It uses electrostatic charges, dry ink (toner) and light. A selenium-coated, photoconductive drum is positively charged. Using a laser or LEDs, a negative of the image is beamed onto the drum, cancelling the charge and leaving a positively charged replica of the original image.
A negatively charged toner is attracted to the positive image on the drum, and the toner is then attracted to the paper, also positively charged. The final stage is fusing, which uses heat and pressure, pressure alone or light to cause the toner to permanently adhere to the paper.
Xerography Was Introduced in 1948
In 1938, electrophotography was invented by Chester Carlson in Queens, New York, and his first of 28 patents was issued in 1940. By 1947, Haloid Corporation and Batelle Development Corporation were working with Carlson, and xerography became official in 1948. A huge breakthrough, it replaced the messy liquid ink of the duplicating machines of the day with a dry, granular ink. In Greek, xero means "dry," and graphy means "write."
"Painting" the Drum
The Model A - 1949
The 1938 Experiment Replicated in 1965
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