Specifications

LED page printers are capable of printing all four colors in a single pass of the drum. Laser printers, on the other hand,
must apply cyan, yellow, magenta, and black colors with separate passes. After the first color is applied, the paper
passes through the mechanism again for the second color, and so forth. Thus, a color LED page printer has the same max-
imum speed rating for both color and black-and-white printing, whereas laser-based color printers print black four times
faster than color pages because only one pass is required for black.
Inkjet Printers
The data interpretation stages of the inkjet printing process are fundamentally similar to those of a
laser printer. The main difference is that, because many inkjets tend to occupy the low end of the
printer market, they are less likely to have the powerful processors and large amounts of memory
found in lasers. You are therefore likely to find more inkjet printers on the market with relatively
small memory buffers that rely on the PC for the majority of their processing activities. These printers
can print graphics using band buffers instead of full-page buffers. Higher-end inkjets, however, can
have virtually the same processing capabilities and memory capacities as laser printers. Because most
low-end inkjet printers rely on the computer for much of the processing, slow computers are likely to
print pages more slowly with a given printer than a faster computer will.
The primary difference between an inkjet printer and a laser printer, however, is the way the image is
applied to the page. Inkjet printing technology is far simpler than laser printing, requires fewer and
less expensive parts, uses less power, and takes up much less space. Instead of an elaborate process by
which toner is applied to a drum and then transferred from the drum to the page, inkjet printers use
tiny nozzles to spray liquid ink directly onto the paper in the same dot patterns used by laser printers.
Inkjet printers print one band of text and graphic data at a time as the printer receives it, as opposed
to the page-oriented laser and LED printer, which must receive the entire page before printing. For
these reasons, inkjet technology is more easily adapted for use in portable printers.
Two basic types of inkjet printing are in use today: thermal and piezo (discussed in the following sec-
tions). These terms describe the technology used to force the ink out of the cartridge through the noz-
zles. The inkjet cartridge typically consists of a reservoir for the liquid ink and the tiny (as small as
one micron) nozzles through which the ink is expelled onto the page. The number of nozzles is
dependent on the printer’s resolution; configurations using anywhere from 21 to 256 nozzles per
color are common. Some printers provide more nozzles in their black-printing cartridges to improve
printing speed. Color inkjet printers use four or more reservoirs with different color inks (cyan,
magenta, yellow, and black are the most common; light cyan and light magenta are added for six-
color printing by some printers for better photo quality). By mixing the different-colored inks, the
printer can produce virtually any color. (Most inkjets use one replaceable cartridge to hold the reser-
voirs for the three basic colors: cyan, magenta, and yellow.)
Thermal Inkjet Printing
Thermal inkjet printers function by superheating the ink in the cartridge to approximately 400°. This
causes vapor bubbles to form inside the cartridge and rise to the top of the reservoir. The pressure
from the vapor forces ink out of the cartridge through the nozzles in tiny droplets that form the dots
on the page. The vacuum caused by the expelled ink draws more ink down into the nozzles, making a
constant stream of droplets as needed.
The thermal type of inkjet printing was the first to be developed and is still the most popular. Because
of the vapor bubbles that form in the cartridge, Canon began calling its inkjet printers BubbleJet, a
name that has become almost synonymous with this technology. This method is also used by
Hewlett-Packard and others. Because of the high heat used by this method, printers that use thermal