Types of scanner...!!

1. SCANNER TYPES
Flatbeds
Flatbed scanners are the best-known and largest selling scanner type, and with good reason.
They're versatile, easy to operate, and widely available. Their popularity for Web publishing
has opened up a huge market, pushing prices for entry level units below $100. At the other end,
professional units for the color graphics market now rival drum scanners in quality. All use the
same basic technology, in which a light sensor (generally a CCD) and a light source, both
mounted on a moving arm, sweep past the stationary document on a glass platen. Automatic
document handlers (ADH) are available on some models, and can increase throughput and
lessen operator fatigue for sets of uniform documents in reasonably good condition. A
specialized variant of the flatbed scanner is the overhead book scanner, in which the scanner's
light source, sensor array and optics are moved to an overhead arm assembly under which a
bound volume can be placed face up for scanning.
Flatbed Scanner Overhead Scanner
Sheet feed Scanners
Sheet feed scanners use the same basic technology as flatbeds, but maximize throughput,
usually at the expense of quality. Generally designed for high-volume business environments,
they typically scan in black and white or gray scale at relatively low resolutions. Documents are
expected to be of uniform size and sturdy enough to endure fairly rough handling, although the
transport mechanisms on some newer models reduces the stress. Using roller, belt, drum, or
vacuum transport, the light sensor and light source remain stationary while the document is
moved past. An important subclass of sheet feed scanners are upright models specifically
designed for oversize documents such as maps and architectural drawings.

2. Sheet feed Scanner
Drum Scanners
Drum scanners produce the highest resolution, highest quality scans of any scanner type, but at
a price. Besides their expense, drum scanners are slow, not suitable for brittle documents and
require a high level of operator skill. Thus they are typically found in service bureaus that cater
to the color pre-press market.
Drum Scanner

3. Microfilm Scanners
Microfilm scanners are highly specialized devices for digitizing roll film, fiche, and aperture
cards. Getting good, consistent quality from a microfilm scanner can be difficult because they
can be operationally complex, film quality and condition may vary, and because they offer
minimal enhancement capability. Only a few companies make microfilm scanners, and the lack
of competition contributes to the high cost of these devices. Specifications for some microfilm
scanners are available at http://www.rlg.org/preserv/diginews/diginews5-3.html#faq.
Microfilm Scanner
Slide Scanners
Slide scanners are used to digitize existing slide libraries as well as photo intermediates of 3-
dimensional objects and documents that are not well-suited for direct scanning, though more
and more such objects will be captured directly by digital camera. The use of transparent media
generally delivers an image with good dynamic range, but depending on the size of the original,

4. the resolution may be insufficient for some needs. Throughput can be slow.
Slide Scanners
Digital Cameras
Digital cameras combine a scanner with camera optics to form a versatile tool that can produce
superior quality images. Though slower and more difficult to use than flatbed scanners, digital
cameras are adaptable to a wide array of documents and objects. Most fragile materials can be
safely captured, though the need to provide external lighting means that light damage may be a
concern. Digital camera technology continues to improve, helped along by the growing
consumer market.
Digital Camera
List the Characteristics Of A Keyboard
The keyboard is an input device that contains keys you press to enter data into a computer.
Desktop computer keyboards usually have from 101 to 105 keys, while keyboards for smaller
computers contain fewer keys. All keyboards have a typing area used to type letters of the
alphabet, numbers, punctuation marks, and other basic characters. Many desktop computer
keyboards also have a numeric keypad designed to make it easier to enter numbers, function
keys programmed to issue commands and accomplish certain tasks, arrow keys used to move
the insertion point (a symbol on the screen that indicates where the next typed character will
display), and toggle keys that can be switched between two different states.