The average person wants a colour scanner for photos or graphics. A small business owner might be looking for a portable scanner for business trips or a black & white scanner to read documents and translate them into editable text. Graphic artists or desktop publishers might be looking for a specialized photo or slide scanner. Armed with the proper information, you'll be able to find a scanner that does just what you ask.

How A Scanner Works
A scanner is a device that captures and converts images to a computer format. Its eyes are an array of photosensitive cells that detect light reflected off or transmitted through the object being scanned. This array of receptors, referred to as a charged-couple device (CCD), measures light intensity and converts it into an electrical charge.

An analogue to digital converter (ADC) is then required to digitize the information, putting into a form your computer can understand. Each cell in the CCD array creates one pixel and for each pixel a certain number of bits is stored. The more bits of information assigned to each pixel the better the image quality.

There are also scanners that use CIS (Contact Image Sensor) technology. With a CCD scanner, the light reflected from the original document passes through a system of mirrors and lenses which redirect the light to the CCD array. In a CIS scanner, the array of image sensors lies just under the document to be scanned so the sensors catch the reflected light directly. CIS scanners are cheaper to manufacture, smaller and more durable, however their image quality is not as good as CCD. They are more suited to cramped desktops and make useful portable scanners.

Flatbed Scanners
Flatbed scanners are constructed with a flat glass plate over the photosensitive array and a cover to go over the glass. You can place paper or objects like open books on top of the glass. Light emitted from under the glass reflects off the object being scanned and is picked up by the moving CCD array in the scan head. Flatbeds are a popular and flexible type of scanner that come in both monochrome and colour. Their only draw back is that they hog a lot of desktop space. Prices for general purpose models can start below $150, for higher image quality the range is $350 plus.

Sheetfed Scanners
Unlike a flatbed scanner, the photosensitive array in a sheetfed scanner is stationary, and the page being scanned is moved over the array. This is a good type of scanner for someone who intends to scan a lot of documents to produce editable text. If you combine a sheetfed scanner with an automatic document feeder (ADF), you don't need to feed in each sheet by hand.

Sheetfeds are available in both monochrome and colour. Although you can feed pictures or small pages into the scanner, the scanned images can get warped so flatbeds are still more flexible. Sheetfed scanners are nicely compact so they're good for limited spaces. You can pick up one of these scanners for under $150. Rapid, high volume business models can get into the thousands.