You might be surprised to learn that a primitive early version of a scanner was invented and used commercially as early as the mid-1800s. Italian Giovanni Caselli, a physics teacher at the University of Florence, developed a device he called the pantelegraph, a combination of "pantograph", a tool that copies drawing, and "telegraph". The pantelegraph used electromagnetic components to scan and reproduce images and transmit them over telegraph lines, something like a fax machine.
In 1857 Caselli travelled to Paris, where French engineer Paul Gustave Froment assisted him in putting the finishing touches on the pantelegraph. The first "pantelegram" was sent from Lyons to Paris in February of 1862. Although the pantelegraph was perfectly capable of transmitting text, it was largely perceived and marketed as a tool for transmitting images.
The device so intrigued Louis-Napoleon Bonaparte III, the nephew and heir of Napoleon the first, that he ensured Caselli had access to the needed telegraph lines. The public gained access to the service in 1863, and Russian Tsar Nicolas I installed the service between his palaces in Saint Petersburg and Moscow in 1864. Almost 5,000 pantelegram messages were sent in its first year of service.
Despite being greeted with great initial enthusiasm, the pantelegraph had some technical limitations, and never really caught on. There are still a few remaining pantelegraphs in existence, and they have been featured in exhibitions at a couple of French museums. In 1982 the Postal Museum in Riquewihr, France ran two pantelegraphs for six hours a day for several months, and they performed flawlessly. To watch a video describing exactly how the pantelegraph works, please visit www.youtube.com.
The pentelegraph was followed by Edouard Belin's Belionograph in 1914. The Belionograph, also designed in France, worked by placing an image on a cylinder, and scanning it with a powerful light containing a photoelectric cell to convert that light into transmittable electrical impulses. This process was later used in facsimile machines. In 1934, Associated Press began using the system to transmit "wire photos".
Modern scanners fall into four main categories: drum scanners, flatbed scanners, film scanners and hand scanners. The first image scanner intended for use with a computer was a drum scanner, developed in 1957 by a US National Bureau of Standards team headed by Russell Kirsch and named after the clear acrylic cylinder on which the original is mounted. Drum scanners spin at high speeds, and a light beam or laser capable of focusing on one pixel moves down the drum one line at a time, sending information to photomultiplier tubes. This process can produce resolutions exceeding 10,000 dpi.
Drum scanners provide the ultimate in scanning quality, colour and resolution, but are very expensive compared to the more commonly used flatbed scanners. Their use is reserved for high-end commercial graphics, museum-quality archiving of photographs, and applications that turn photos into posters and over-sized images. The item to be scanned must be thin and flexible enough to be wrapped around the drum.
Electronic flatbed scanners are usually flat devices with a hinged lid over a glass pane on which you lay the documents you want to scan. The device scans the image using a light or a contact image sensor (CIS). Single-pass scanners capture the colours red, green and blue by moving the light source over the image once. Three-pass scanners use three passes, one pass each for red, green and for blue. The single-pass scanners are faster, but the three-pass scanners are generally more accurate.
Some flat bed scanners include a sheet feeder. There are also stand-alone sheet fed scanners that do not have a cover or glass plate. Flatbed scanners are available in entry level, mid-level and high-end models. A basic scanner is often incorporated into another device, such as a combination-held printer, photocopier and fax machine. High-end flatbed scanners are alternatives to drum scanners for professional use.
A hand image scanner comes in document or 3D forms. These are manually moved across a document, object, or image to be scanned. Hand scanners are smaller, portable and inexpensive, but can only scan small areas at a time and, unless they're high end, may produce mediocre results.
One affordable yet good quality portable scanner is the Scan2Docx. This lightweight (500 g or 1.2 lb), foldable, high-resolution (200 dpi) camera-based scanner can scan an entire page in two seconds. An intuitive MS Windows software application allows users to share scans immediately with a simple drag and drop. The Scan2Docx portable scanner can scan pages, books, magazines and even 3D objects.
Specialized scanners include film and slide scanners, business card scanners, and stand alone sheet fed oversize digitizers for very large originals. What's on the horizon? New scanning technologies are combining 3D scanners with digital cameras to create full-color, photo-realistic 3D models of objects.
The Pantelegraph, Mother of the Scanner is written by Craig Hollingum. Craig Hollingum has been in the Document Imaging business for well over half of his life. He has been involved in Micro Com Systems Ltd on an evolutionary path as an employee/partner/sole owner since 1982. For more information, please visit Craig Hollingum's Google+.