
Most scanners on the market today are
flatbed scanners, usually for scanning documents of A4 though A3 paper sizes. There are two of types of flatbed scanner types available: reflective scanners and transparent scanners.
When you place an item such as a book or piece of paper on the glass plate of a flatbed scanner, the document is illuminated from underneath, and the scanner users mirrors to copy an image of the document on the plate to a digital file. This is known as reflective scanning.
Transparent scanning is used for items that are see-through, for example slides, and these need to be placed in a special box that clips onto the glass of a flatbed scanner. A special light then illuminates these items inside the lid, and the item can be slowly scanned.
These transparency adapters can either be built into the top of a flatbed scanner or come as separate attachment. This is not a standard feature on flatbed scanner models though, so if scanning transparent items is important to you, make sure you verify that your chosen scanner can accommodate this.
Flatbed scanner models will use either CCD (charge-coupled device) or CIS (contact image sensor) sensor technology. The former is slightly older technology, and CIS is becoming more prevalent. Even though CIS tends to produce a slightly lower quality scanned image, it allows for smaller devices and uses less power than a CCD scanner, and so CIS scanner models can be powered via a USB cable and do not need an additional power source.
There are other types of scanner available.
Handheld scanner models can be useful if you travel and need to scan documents frequently, as these are portable and save images to a memory card rather than needing to be attached to a PC. These are often used by students, or professionals who frequently need to take many notes, as they can be used to scan books or periodicals easily.
Sheetfed scanner models, which used to be very popular, are still available. These require users to feed an item individually through a narrow feeder slot, and are thus are only suitable for flat documents.
Film scanner models are primarily designed for professional use; these are specifically designed to scan film negatives, slides, or APS film. Most will focus on one type of film, so if this is what you need, take care that the scanner you choose can cope with the film you are using.
You can also buy multi-feature or
'all-in-one' machines that combine a printer, scanner, and fax machine, which often appeals to small business owners, as they are a more efficient use of office space than a number of separate items.