In computing, an image scanner—often abbreviated to just scanner— is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop (or flatbed) scanner where the document is placed on a glass window for scanning. Hand-held scanners, where the device is moved by hand, have evolved 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 category of scanner is digital camera scanners, which are based on the concept of reprographic cameras. Due to increasing resolution and new features such as anti-shake, 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).

                 Thermal Bubble Printing Of the several technologies used by inkjet printer manufacturers, the most popular is the bubble jet. It has been given this name because inside the bubble jet print head, tiny resistors generate heat that vaporises the ink to create a bubble. The expansion that creates the bubble causes a droplet to form and eject from the print head. The bubble jet print head typically has 64 or 128 tiny nozzles, and all of them can fire a droplet simultaneously.

                  Each nozzle is approximately 70 microns, or about the same diameter as a human hair. Dot sizes vary between 50 and 60 microns in diameter. The smallest dot size visible to the naked eye is around 30 microns. The nozzles are capable of delivering drops with a volume of around 8 - 10 picolitres. Dye-based cyan, magenta and yellow inks are normally delivered via a combined colour print-heads.

                 Several small colour ink drops - typically between four and eight - can be combined to deliver dots of varying sizes. This also achieves a bigger palette of non-halftoned colours and smoother halftones. Black ink, which is generally based on bigger pigment molecules, is delivered from a separate print-head in larger drop volumes of around 35pl. Resolution varies between 300 and 600 dots per inch, with enhanced resolutions on some printers of 1200dpi.

                 A technology that relies on heat, such as thermal, creates two limitations on performance. First, because the firing process is heat based, the ink must be resistant to heat. And second, because of the heating, there is a secondary need for a cooling process, which affects print speed. Print speed is chiefly a function of how quickly the nozzles can be made to fire ink drops and the width of the swath across the paper printed by the print-head. This typically translates into print speeds of between 4 to 8 pages per minute for monochrome text and 2 to 4ppm for colour text and graphics.