SCANNER

A scanner is a device that analyzes a physical image (such as a photograph, printed text, or handwriting) or an object (such as an ornament) and converts it to a digital image.

Most scanners today are variations of the desktop (or flatbed) scanner The flatbed scanner is the scanner most people will have as it is simple to use and effective in its purpose. Hand-held scanners, where the device is moved by hand, were briefly popular but are now not used due to the difficulty of obtaining a high-quality image. Both these types of scanners use a charge-coupled device (CCD) as the image sensor, whereas a drum scanner uses a photomultiplier tube as the image sensor.

Other types of scanners are planetary scanners, which take photographs of books and documents, and laser range scanners, for producing three-dimensional models of objects.

Scanners have become an important part of the home office over the last few years.

Scanner technology is everywhere and used in many ways:

• Flatbed scanners, also called desktop scanners, are the most versatile and commonly used scanners. In fact, this article will focus on the technology as it relates to flatbed scanners.
• Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. A sheet-fed scanner looks a lot like a small portable printer.
• 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.

Anatomy of a Scanner

Parts of a typical flatbed scanner include:

• Charge-coupled device (CCD) array
• Mirrors
• Scan head
• Glass plate
• Lamp
• Lens
• Cover
• Filters
• Stepper motor
• Stabilizer bar
• Belt
• Power supply
• Interface port(s)
• Control circuitry