Specifications

Sheetfed Scanners—”Faxing” Without the Fax
Hand scanners have been replaced by more powerful, less fussy scanner technologies that are now
often similarly low in price.
A sheetfed scanner uses motor-driven rollers to pull the document or photograph to be scanned past a
fixed imaging sensor. The design is virtually identical to the scanner built into fax machines. This fact
made it easy for even the first multifunction office machines (see preceding sections) to incorporate
limited scanning capabilities.
Sheetfed scanners, such as Visioneer’s PaperPort, work well for letter-sized documents. In addition,
color-compatible models with scanning resolutions of 300dpi or above have also proved competent at
handling photographs.
Advantages of the Sheetfed Scanner
■ Easy interfacing. Almost all sheetfed scanners take advantage of the “hidden” bidirectional fea-
tures of the parallel (LPT) port and provide a second port to enable printers to daisy-chain to
the scanner.
■ Low cost. Because the sheetfed scanner uses a simple, rigid imaging device and a straightforward
motorized-roller mechanism, its production and selling costs are low.
■ Size. The sheetfed scanner is very compact and portable; it can easily fit into a briefcase. Some
vendors produce ultra-thin models specially designed for use with portable computers.
Drawbacks of the Sheetfed Scanner
■ Scanning limited by resolution, origins of mechanism. As an outgrowth of fax imaging, sheetfed
scanners were originally intended for line art or text scanning only. Although later models also
could support grayscale and color scanning, the mechanism’s limitations mean that resolutions
are typically limited to 300dpi–400dpi. This is adequate for same-sized scanning but precludes
serious enlargements of small originals.
■ Limited media handling. Because the sheetfed scanner is essentially a computer-controlled fax
scanner, it’s subject to the same limitations as a fax machine. It can’t handle books or even any-
thing thicker than a piece of paper. It might jam or pull the document through unevenly, pro-
ducing some unintentionally “creative” effects. It can’t work with any type of transparent
media, such as negatives or slides, and will even have problems with smaller than letter-sized
documents or snapshot-sized photos.
Although some late-model sheetfed scanners were supplied with a transparent sleeve to hold odd-
sized originals, their inability to work with anything beyond individual sheets is a serious limitation.
For these reasons, sheetfed scanners are less popular than flatbed scanners today but continue to be
an important part of the jack-of-all-trades multifunction office machine.
Flatbed Scanners
Take the toner, drum, and paper feed off a copier and add a computer interface, and you have the
basic understanding of a flatbed scanner—the current favorite among after-the-fact imaging technolo-
gies. Recent developments have pushed flatbed scanners to new heights in optical (true) resolution
while reducing the price: In many cases you can buy a scanner with 1,200dpi or higher resolution for
about one-third the cost of a model with 600dpi resolution just a couple of years earlier.