ĭrum scanners capture image information with photomultiplier tubes (PMT), rather than the charge-coupled device (CCD) arrays found in flatbed scanners and inexpensive film scanners. The black and white image had a resolution of 176 pixels on a side. The first image ever scanned on this machine was a 5 cm square photograph of Kirsch's then-three-month-old son, Walden. It was built in 1957 at the US National Bureau of Standards by a team led by Russell A. The first image scanner developed for use with a computer was a drum scanner.
Color photos were sent as three separated RGB filtered images consecutively, but only for special events due to transmission costs. They send a linear analog AM signal through standard telephone voice lines to receptors, which synchronously print the proportional intensity on special paper. It was used by news agencies from the 1920s to the mid-1990s, and consisted of a rotating drum with a single photodetector at a standard speed of 60 or 120 rpm (later models up to 240 rpm). In Europe, services similar to a wirephoto were called a Belino. Édouard Belin's Belinograph of 1913, scanned using a photocell and transmitted over ordinary phone lines, formed the basis for the AT&T Wirephoto service. It could transmit handwriting, signatures, or drawings within an area of up to 150 × 100 mm. It used electromagnets to drive and synchronize movement of pendulums at the source and the distant location, to scan and reproduce images. The pantelegraph (Italian: pantelegrafo French: pantélégraphe) was an early form of facsimile machine transmitting over normal telegraph lines developed by Giovanni Caselli, used commercially in the 1860s, that was the first such device to enter practical service. Modern scanners are considered the successors of early telephotography and fax input devices. The detection is done via CCD or a photomultiplier tubes.īelinograph BEP2V wirephoto machine by Edouard Bélin, 1930 These scanners are high-resolution systems (up to 1 µm/ pixel), similar to microscopes. In the biomedical research area, detection devices for DNA microarrays are called scanners as well. In 2010 scanning technologies were combining 3D scanners with digital cameras to create full-color, photo-realistic 3D models of objects. Digital cameras offer advantages of speed, portability and non-contact digitizing of thick documents without damaging the book spine. Resolution is sufficient for less demanding applications. When compared to a true scanner, a camera image is subject to a degree of distortion, reflections, shadows, low contrast, and blur due to camera shake (reduced in cameras with image stabilization). All these scanners produce two-dimensional images of subjects that are usually flat, but sometimes solid 3D scanners produce information on the three-dimensional structure of solid objects.ĭigital cameras can be used for the same purposes as dedicated scanners. Non-contact planetary scanners essentially photograph delicate books and documents. A rotary scanner, used for high-speed document scanning, is a type of drum scanner that uses a CCD array instead of a photomultiplier. Modern scanners typically use a charge-coupled device (CCD) or a contact image sensor (CIS) as the image sensor, whereas drum scanners, developed earlier and still used for the highest possible image quality, use a photomultiplier tube (PMT) as the image sensor. Mechanically driven scanners that move the document are typically used for large-format documents, where a flatbed design would be impractical. 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. Commonly used in offices are variations of the desktop flatbed scanner where the document is placed on a glass window for scanning. Documents or images are placed face-down beneath the cover (shown closed here).Īn 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.
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