MGMT 1050 Lecture Notes - Lecture 6: Xerography, Gunpowder, Real Image
MGMT 1050 Tutorial 6 Notes – Operation of a Laser Printer
Introduction
• In general, the intensity, or brightness, of the dots is fixed, unlike the pixels in a display,
which can take on an infinite range of brightnesses.
• Thus, to create a gray scale or color scale, it is necessary to congregate groups of dots
into a single equivalent point
• Print different numbers of them to approximate different color intensities.
• An example of this is shown.
• Today, the prevalent form of printing for most applications is laser printing.
• Laser printing is derived from xerography.
• The major difference is that the image is produced electronically from the computer
using a laser or light-emitting diodes
• Rather than scanning a real image with a bright light, as in a copy machine.
• A description of the steps in the operation of a laser printer is shown.
• Color images are produced by printing the sheet four times with different colored
toners.
• A laser is fired in correspondence to the dots that are to be printed.
• A spinning mirror causes the dots to be fanned out across the drum.
• The drum rotates to create the next line, usually 1/300th or 1/600th of an inch.
• The drum is photosensitive.
• As a result of the laser light, the drum will become electrically charged wherever a dot is
to be printed.
• As the drum continues to rotate, the charged part of the drum passes through a tank of
black powder called toner.
• Toner sticks to the drum wherever the charge is present.
• Thus, it looks like the image.
• A sheet of paper is fed toward the drum.
• A charge wire coats the paper with electrical charges.
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