What is a Scanner

ScannerA 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.