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a section of black dye. A print head containing thousands of heating elements, capable of precise temperature control, moves across the film, vaporizing the dyes and causing them to soak into specially coated paper underneath before cooling and reverting to a solid form. This process requires one pass per page for each color. Some printers also use a final finishing pass that applies a protective laminate coating to the page. Figure 22-7 shows how a dye-sublimation printer works.

Documents printed through the dye-sublimation process display continuous-tone images, meaning that the printed image is not constructed of pixel dots but a continuous blend of overlaid differing dye colors. This is in contrast to other print technologies’ dithered images, which use closely packed, single-color dots to simulate blended colors. Dye-sublimation printers produce high-quality color output that rivals professional photo lab processing.

Figure 22-7 The dye-sublimation printing process

Thermal Printers

Thermal printers use a heated printhead to create a high-quality image on special or plain paper. You’ll see two kinds of thermal printers in use. The first is the direct thermal printer, and the other is the thermal wax transfer printer. Direct thermal printers burn dots into the surface of special heat-sensitive paper. If you remember the first generation of fax machines, you’re already familiar with this type of printer. Many retail businesses still use it as a receipt printer. Thermal wax printers work similarly to dye-sublimation printers, except that instead of using rolls of dye-embedded film, the film is coated with colored wax. The thermal printhead passes over the film ribbon and melts the wax onto the paper. Thermal wax printers don’t require special papers like dye-sublimation printers, so they’re more flexible and somewhat cheaper to use, but their output isn’t quite as good because they use color dithering.

Laser Printers

Using a process called electro-photographic imaging, laser printers produce high-quality and high-speed output of both text and graphics. Figure 22-8 shows a typical laser printer. Laser printers rely on the photo conductive properties of certain organic compounds. Photoconductive means that particles of these compounds, when exposed to light (that’s the “photo” part), will conduct electricity. Laser printers usually use lasers as a light source because of their precision. Some lower-cost printers use LED arrays instead.

Figure 22-8 Typical laser printer

The first laser printers created only monochrome images. Today, you can also buy a color laser printer, although the vast majority of laser printers produced today are still monochrome. Although a color laser printer can produce complex full-color images such as photographs, they really shine for printing what’s known as spot color—for example, eye-catching headings, lines, charts, or other graphical elements that dress up an otherwise plain printed presentation.

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NOTE Some printers use consumables—such as ink—at a much faster rate than others, prompting the industry to rank printers in terms of their cost per page. Using an inexpensive printer (laser or inkjet) costs around 4 cents per page, while an expensive printer can cost more than 20 cents per page—a huge difference if you do any volume of printing. This hidden cost is particularly pernicious in the sub-$100 inkjet printers on the market. Their low prices often entice buyers, who then discover that the cost of consumables is outrageous—these days, a single set of color and black inkjet cartridges can cost as much as the printer itself, if not more!

Critical Components of the Laser Printer

The CompTIA A+ certification exams take a keen interest in the particulars of the laser printing process, so it pays to know your way around a laser printer. Let’s take a look at the many components of laser printers and their functions (Figure 22-9).

Figure 22-9 Components inside a laser printer

Toner Cartridge The toner cartridge in a laser printer is so named because