General laser printer technology – Printronix L1024 User Manual

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Introduction

General Laser Printer Technology

The operation of a laser printer is somewhat different than that of an impact

printer. They produce an entire page at once, compared to line printers, which

produce complete character lines.

NOTE: If the software application fails to give a form feed at the end of the

data, and the data does not exceed the selected lines per page

setting, the page will not print. Rather, it will remain in memory.

The laser printer has two basic functional parts: the engine and the controller.

The engine is responsible for the mechanical aspects of producing the page. The

controller controls the printer and is responsible for electronic data

manipulations.

NOTE: Laser printers can not print to the physical edge of the paper. If the

document image runs to the edge of the paper, portions of the image

may be lost.

The electrophotographic printing process, shown in Figure 1–2, consists of the

following steps:

Charging: The charge corona is a thin wire electrode that extends

across the width of the media. This electrode places a high–voltage

electrostatic charge on the organic photoconductor (OPC) drum.

Imaging: Based on data received from the host computer, a bit–mapped

image of the page is generated in random access memory (RAM) on the

controller (not shown).

Exposing: The laser scanning unit (LSU) exposes areas of the OPC

which are to be imaged (i.e., black). This forms a latent image of the

bit–mapped data. This image is made up of charged and uncharged

areas.

Developing: The latent image areas of the OPC attract toner from the

developer unit to form the developed image on the OPC drum. Since the

charged areas of the drum have the same charge as the toner, they repel

the toner.