|Microtek ScanMaker 3840 flatbed scanner. Mamun2a 09:50, 4 September 2006 (UTC) http://commons.wikimedia.org/wiki/File:Scaner.jpg|
But first introduction to scanning took place years and years ago with the introduction of optical scanning devices for reproducing photos and other documents. My first scanning experience was with the facsimile copies called telecopying or FAX for short. There was no intermediate file of the information in the original, the image of the sheet was sent directly to a similar machine that received and printed out the image over a telephone line. You would put the document into a rotating drum and the light would make an analog image of the document or photo and send it, where the receiving device would use the signal to reproduce the document on light or heat sensitive paper. These copies tended to fade over time rather dramatically. FAX machines are still ubiquitous in most offices and some homes, but the technology has advanced and most of the printing mechanisms use a laser printer for output on regular paper.
The main difference between a FAX machine and a scanner is that if a document is "scanned," a digital image is made and stored in a computer file. The resultant digital image can be stored or transmitted to another computer. The basic principles of operation for all scanners, in all the iterations of shapes and sizes, is essentially the same. Here is the summary describing image scanners from Wikipedia:
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.Dedicated image scanners are starting to be replaced by cameras due to the increase in the quality of camera images. But today, there is a huge variety of types of scanners. Here is a summary of some of the types currently available:
Modern scanners typically use a charge-coupled device (CCD) or a Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use aphotomultiplier 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.
Mobile or handheld scanners:
Pro: Lightweight. Some models run on batteries and will scan directly to a flash drive or memory chip. Easy to operate and relatively good quality. Usually quite inexpensive. (Note: some mobile scanners are classified by the manufacturers as sheetfed scanners). They can be purchased for around a $100 or more, depending on the features included with the scanner.
Con: Usually very slow. Some require additional software to stitch the images together into a complete picture. Some models are very limited in the file format to which they will save the files they create. Usually marginal quality for scanning photographs. No ability to scan film, slides or negatives.
Pro: Can be very fast. Can be very high quality, and the more expensive models can scan larger-size input. Usually produce good quality scanned images. Most models will support a variety of file types, including those suitable for archival use. The price of scanners has dropped dramatically over the years and letter sized, flatbed scanners begin at less than $50.
Con: Lower-priced models may lack speed and/or paper handling ability. Few models will scan film, slides or negatives. Usually faster scanning equates to a higher purchase price.
Pro: Very high quality scans. Much slower than sheetfed scanners but still faster than most mobile scanners. They are usually higher quality and support more file formats than mobile scanners. You can get a very high quality flatbed scanner with a film option for around $200. Dedicated film or slide film scanners can be very expensive i.e. over $2000,
Con: Limited to scanning one larger document at a time or several small documents or photographs. Even the fastest flatbed scanner is much slower than a sheetfed scanner. Some manufacturers sell their flatbed scanners as “document” scanners. There is not a clear distinction between document scanners and flatbed scanners for some models.
Pro: With the combination of several machines in one, desktop space is minimized. There is a measure of convenience in having a number of functions combined in one machine. Usually, this machine is billed as a FAX/Copy/Scanner/Printer. Some actually do all three functions fairly well. The supplies for the printing function can cost more than these machines.
Con: The obvious–you cannot scan while you print and or use any of the other functions of the device. So if you want to do anything else with the machine while it is involved in one of the functions, you just have to wait until it is finished. Sometimes the scanning portion of the machine is of much less quality than a comparably priced flatbed scanner. Do not mistake these multi-function office machines for sheetfed document scanners.
I have used all four of these types of machines. I primarily use a dedicated flatbed scanner, such as an Epson or Canon, for my scanning projects. I have a high speed Canon sheetfed scanner for archiving documents, It does not do a good job with photos. I am moving over to using my high Megapixel digital camera instead of a flatbed scanner to achieve higher quality images. More about this later.