A laser printer employs technology just like a photocopy machine. A laser beam focuses a positively charged selenium-coated rotating drum. The laser gum removes the positive charge from the drum except for the area to be printed.
In this way, the laser draws the letters and images to be printed as a pattern of electrical charges that is called an electrostatic image. The negatively charged black toner powder first adheres to this positively charged area (image) on the drum from where it is transformed to the rolling white paper.
Before the paper rolls under the drum, it is given a positive charge stronger than the positive charge of the electrostatic image, so the paper can pull the toner powder away. The paper is then subjected to mild heating to melt and fix the loose toner on the paper. The laser printer is mainly a bi-level printer.
An Inkjet printer is a non-impact printer that places extremely small droplets of ink onto paper to create an image. These printers are popular because they cost less but generate attractive graphics output.
The dots sprayed on paper are extremely small (usually between 50 and 60 microns in diameter) and positioned very precisely with resolutions of up to 1440×720 dpi. The dots can have different colours combined to create photo-quality images. The core of an Inkjet printer is the print head that contains a series of nozzles that are used to spray drops of ink.
An Electrostatic Printer has many print head, actually covering the entire 36 media width. So, instead of a single print head moving across the width of the media. The electrostatic printer prints an entire width of the page at one time.
The media (paper, vellum, film) is electrostatically charged. The toner solution is circulated past the media and sticks to the energized portion of the media, thus producing a very fast high-quality image. The printer creates colour prints by breaking colour data down three basic colours (cyan, magenta, and yellow) plus black, and printing one colour at a time. In 5-pass print mode, combinations of cyan, magenta, yellow and black provide a wide range of different colours.
A plotter is a vector device that can directly reach specific positions on printer paper without raster scan device. In colour plotters, the carriage accommodates a number of pens with varying colours and widths.
The microprocessor in the plotter receives instructions from the host computer and executes commands like ‘move’ carriage to a given position with pens up and drawing geometric entities like a point, line, arc, circle, etc.