A Scanner is an input device that capture/scans documents such as images from photographic prints, posters, magazine pages, and similar sources for computer editing and display. This creates an electronic version of the document that can be viewed and edited on a computer.
Very high resolution scanners are used for scanning for high-resolution printing, but lower resolution scanners are adequate for capturing images for computer display. Most scanners are flatbed devices, which means they have a flat scanning surface.
The four common scanner types are:
+ Flatbed Scanners
+ Sheet-fed Scanners
+ Handheld Scanners
+ Drum Scanners
A Flatbed Scanner provides a flat, glass surface to hold a sheet of paper, book or other object for scanning. The scan head is moved under the glass. Flatbed Scanners often come with sheet feeders for scanning multiple sheets of paper rather than one at a time. Because of their large size capacity and ability to scan thick objects, flatbed scanners are more versatile than sheet-fed scanners.
A Sheet-fed Scanner allows only paper to be scanned rather than books or other thick objects. It moves the paper across a stationary scan head. Contrast with flatbed scanner, handheld scanner and drum scanner.
A Handheld Scanners is moved by hand over the material being captured. Handheld Scanners are small and less expensive than their desktop counterparts but partially rely on the user’s dexterity to move the unit across the paper. It is as the name suggests, refers to an electronic device that performs the same tasks as that of a flatbed scanner. It is smaller, portable versions of their desktop cousins.
Drum Scanners used to capture the highest resolution from an image and used by the publishing industry to capture incredibly detailed images. They use a technology called a photo-multiplier 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.
Photographs and transparencies are taped, clamped or fitted into a clear cylinder (drum) that is spun at speeds exceeding 1,000 RPM during the scanning operation. Contrast with flatbed scanner, sheet-fed scanner and handheld scanner.