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Unformatted text preview: takes about 20 seconds to scan a document of size
21 cm x 28 cm. 2. Hand-held scanner. As shown in Figure 9.9, a hand-held scanner has a set of light
emitting diodes encased in a small case that can be conveniently held in hand during
operation. To scan a document, the scanner is slowly dragged from one end of the
document to its other end with its light on. The scanner has to be dragged very steadily
and carefully over the document, otherwise the conversion of the document into its
equivalent bit map will not be correct. Due to this reason, hand-held scanners are used
only in cases where high accuracy is not needed. They are also used when the volume of
documents to be scanned is low. They are also much cheaper as compared to flat-bed
Optical Character Recognition (OCR) Device
We saw in the description above that image scanners may be used to input a wide variety
of documents including pictures, graphics, typed text, or handwritten text. When they are
used for inputting text documents (typed c handwritten), they have the following two
1. Since the input document is stored as an image instead of text, it is not possible to do
any word processing of the document (the computer cannot interpret the stored document
as letters, number and special characters).
2. The storage required for storing the document as an image is several times more than
that required fc storing the same document as a text. For example, a page of printed text
having 2000 characters can be stored as 2000 bytes using the ASCII representation. A bit
map image representation of the same document will require 10 to 15 times more storage
depending on the resolution (granularity) of gri points.
The OCR technology is used to overcome these limitations. In this case, the scanner is
equipped with a character recognition software (called OCR software) that converts the
bit map images of characters to equivalent ASC codes. That is, the scanner first creates
the bit map image of the document and then the OCR software translate the array o...
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- Spring '14