 |
A Scanner is a computer peripheral device that allows a user
to take an image and/or text printed on paper and convert it into
a digital file, allowing the computer to read and/or display the
scanned object. A scanner is commonly connected to a computer USB,
Firewire, Parallel or SCSI port.
|
| There are several types
of SCANNER:
- Flatbed scanner - . It consists of a board
on which you lay books, magazines, and
other documents that you want to scan. It looks like a photocopy
machine. They are also called desktop scanners, They are the most
versatile and commonly used scanners.
- Sheet-Feed scanner – it is large scanner
which you can feed papers. It is also
called desktop scanners. These scanners are excellent for loose
sheets of paper, but they are unable to handle bound documents.
It scanner looks a lot like a small portable printer.
- Overhead scanners (also called copyboard scanners)
look somewhat like
overhead projectors. You place documents face-up on a scanning
bed, and a small overhead tower moves across the page.
- Handheld scanners use the same basic technology
as a flatbed scanner, but
rely on the user to move them instead of a motorized belt. This
type of scanner typically does not provide good image quality.
However, it can be useful for quickly capturing text.
- Drum scanners are used by the publishing industry
to capture incredibly
detailed images. They use a technology called a photomultiplier
tube (PMT). In PMT, the document to be scanned is mounted on a
glass cylinder. At the center of the cylinder is a sensor that
splits light bounced from the document into three beams. Each
beam is sent through a color filter into a photomultiplier tube
where the light is changed into an electrical signal.
|
