Printers are one of the most popular forms of output of a computer system! You use your printers when you want to print an essay you typed up for your English class, when you want to print out a picture your aunt e-mailed you, and when you want to print out a letter you typed to your grandfather. Printers are an important part of your home office system, and are used to perform a variety of tasks!
Printers are devices that put your text documents or computer-generated images to paper. Printers can be classified in a few different ways:
2. Fully Formed vs. Dot-Matrix Characters:
3. Character at a Time vs. Line at a Time:
In this section, we will discuss in detail the two most common types of printers used today-the inkjet printer and the laser printer.
Inkjet printers use dot-matrix characters. These dots are formed by spraying ink directly onto the paper through a small nozzle. There are two major types of inkjet printers:
Drop on demand printers work exactly as their name describes. Dozens of hair-fine nozzles are vertically lined up, and on demand, they will spray ink. To form a character, certain nozzles are opened up by electrical impulses, and droplets of ink are ejected onto a piece of paper. The nozzles move horizontally to the next column until a complete character is formed.
Continuous Inkjet (CIJ) Printers:
Continuous inkjet printers continuously pump ink through a nozzle. There is a continuous stream of ink that is circling the print head and the body of the printer. First, the ink passes through a tube where the droplets are electrically charged. Electrons guide the ink droplets so they are ejected in the right positions to form a character. Ink that is not in used return to a reservoir, from which it is recycled and reused.
A key characteristic of inkjet printers is their ability to print in color. This is one of the reasons why they are so popular in the home and office. Printers use the three primary subtractive colors of cyan, magenta, and yellow. Then, they use a process known as dithering. Dithering is when the primary colors are positioned close together so that different combinations of the cyan, magenta, and yellow can create a whole spectrum of additional colors! Some printers are equipped with three colors, while others with four. Those with three contain only cyan, magenta, and yellow. These printers cannot switch between black and white text and color documents. Other printers have four colors-cyan, magenta, yellow, and black. These can easily switch between black and white documents and color documents!
Laser printers are printers that make use of static electricity. In case you don't know what static electricity is, static electricity is the same stuff that creates lightning and that makes your clothes stick to each other when they come out of the dryer. It is basically an electrical charge that builds up inside an insulated object. You might be wondering how laser printers could possibly use electricity to print letters and characters on a sheet of paper.
First, it is important to know that the core of a laser printer is the photoreceptor. This is a small rotating drum that has a coating on it. This coating allows it to hold either a positive or a negative electrostatic charge. Initially, the photoreceptor is given a positive charge. It gets this positive charge by a special electrically charged wire called the charge corona wire.
Courtesy of The PC Tech Guide
Copyright (c) Dave Anderson.
A laser beam is shined on the photoreceptor as it revolves. This beam discharges areas of the positively charged drum. Using a complex system of mirrors and lenses, the areas that the beam discharges is made to resemble the characters and letters that are to be printed. Then, as the drum continues to rotate, it moves into the laser toner, which is a fine black powder. The toner is positively charged, and thus is attracted to the portions of the photoreceptor that have been discharged by the laser (if you didn't already know, opposites attract in the scientific world).
The drum then rolls over a sheet of paper, which has been given a strong negative charge by a wire called the transfer corona wire. The toner then sticks to the paper, and thus the image to be printed is transferred onto a sheet of paper. To keep the powdery toner from brushing away, heat is applied, permanently adhering the toner to the paper. This is why the paper is warm when it comes right out of a laser printer!
Most laser printers are specifically
designed to print in only black ink. However, there are some laser printers
that can print in color. Like inkjet printers, colored laser printers have
four colors-cyan, magenta, yellow, and black. Using different combinations
of these four colors, all the colors in a color spectrum can be created!
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