Page 49 - Computer

These are the most common scanners Sheet-fed scanners
in homes and offices. The document These are digital imaging systems
to be scanned is placed face down on specifically designed for scanning loose
the glass surface of the scanner. The sheets of paper. They work as flatbed Computer Science
scanning head and the light source scanners, except that a document is fed
FOR ONLINE READING ONLY
under the glass automatically scan the through the scanner and moves along
document at a constant speed. Scanners the beam to be read. These scanners are
can be multi-purpose as they can scan not useful for books but for single sheets
flat originals of various sizes. They can only (see Figure 3.8).
also be connected to a document feeder
to scan multipage documents. Figure 3.6
illustrates a flatbed scanner.

Figure 3.6: Flatbed scanner
Figure 3.8: Sheet-fed scanner
Drum scanners Advantages of scanners
These are special scanners used to scan
reflective and transparent materials at (i) They produce accurate and high-
extremely high quality. These scanners resolution images.
provide high-quality, detailed features, (ii) Scanned images can easily be
dynamic range, and colour interpretation shared, added to an electronic
of the scanned materials. Figure 3.7 document, or edited.
presents a drum scanner. Disadvantages of scanners

(i) Most scanners can only scan flat
objects.
(ii) The quality of scanned items may
differ from that of the original one.
(iii) Some scanners are relatively slow.

Things to consider when using scanners
(i) Scanned images may lose their
original quality based on the type
Figure 3.7: Drum scanner of scanner used.

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Student’s Book Form One