Image Scanner

Scanner is a tool that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variants of the desktop (or flatbed) scanner where the document is positioned on a glass window for scanning. Hand-held scanners, where the gadget is moved by hand, have developed from text scanning "wands" to 3D scanners used for industrial design, reverse engineering, test and measurement, orthotics, gaming and other applications. Mechanically driven scanners that move the document are typically used for large-format documents, where a flatbed design would be impractical.

Modern scanners typically use a charge- coupled device (CCD) or a Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor. A rotary scanner, used for high-speed document scanning, is another type of drum scanner, using a CCD array instead of a photomultiplier. Other types of scanners are planetary scanners, which take photographs of books and documents, and 3D scanners, for producing three-dimensional models of objects.

Another type of scanner is digital camera scanners, which are based on the concept of reprographic cameras. The increasing of technology resolutions and new features digital cameras have become an attractive alternative to regular scanners. While still having disadvantages compared to traditional scanners (such as distortion, reflections, shadows, low contrast), digital cameras offer advantages such as speed, portability and gentle digitizing of thick documents without damaging the book spine. New scanning technologies are combining 3D scanners with digital cameras to create full-color, photo-realistic 3D models of objects.

In the biomedical research area, detection devices for DNA microarrays are called scanners as well. These scanners are high-resolution systems (up to 1 µm/ pixel), similar to microscopes. The detection is done via CCD or a photomultiplier tube (PMT).

More about Image Scanners

An image scanner is a device which scans pictures, text or objects and converts them to digital images. The basic types of image scanners are flatbed, hand, film and drum scanners. Flatbed scanners are what we call Xerox machines, in which an object or document is placed on a glass pane and an opaque cover is lowered over it. A sensor and light moves along the pane, reflecting off the image placed on the glass. The cover prevents other light from interfering and the image becomes visible to the detector.

Once an image is scanned into an image scanner, the data must be processed and sent to a computer. Most scanners read red-green-blue color from the color array. The depth of color depends on the array characteristics, but is typically 24 bits at least. Higher quality models have a color depth of 48 bits or more. The pixels per inch measures the resolution of the image.