Whether you're a graphic designer seeking high-quality reproduction, a Webmaster looking to digitise your snaps or if you just want to save time through OCR, there's a device out there for you. Mike Bedford lifts the lid on scanners

Back in the Seventies, experts advised businesses to prepare for the paperless office. No more letters in the post, no printed reports, no paper magazines or journals, no more newspapers -- in the future, all we would need or want would be a fleeting image on a computer screen. How naive that suggestion sounds today. Far from banishing paper, modern technology has caused a huge increased in the number of trees society uses. Just consider the amount of paper a large office sends for recycling each month. Or take a look at the racks of magazines on every conceivable subject in a large newsagent; it really doesn't appear that the human race is likely to abandon its love affair with the printed page in the near future.

Whether we like it or not, and despite the growth of the Internet, a significant proportion of information will continue to appear, first and foremost, on paper. No wonder we've seen such a growth in scanner sales over the last few years. In this article we'll present an overview of the scanner market by describing the different types available, and giving guidance on which are most suitable for various applications. We will, of course, make reference throughout to specific products in the direct market.

Before we look at the products, a few words on scanner technology are required, and on the most common type -- flatbed scanners -- in particular. A flatbed scanner is a unit with a glass screen, on to which the document is placed face-down, and a lid which closes over the document during scanning. More advanced units have a sheet feeder, which transfers documents one at a time from the input tray to the glass and, after scanning, moves them to an output tray. Below the glass is a bright lamp illuminating the document, and the scanning mechanism, which samples the colour at thousands or millions of points across the document surface.

With an optional transparency adapter, available on some scanners, the light below the glass is disabled and a light above the original is illuminated. This permits to be scanned by transmission of light rather than reflection. The scanning mechanism consists of a charge coupled device (CCD) and a means by which that CCD can be moved, in fine increments, down the page. The CCD measures the light intensity and colour at thousands of points in a thin strip across the page, and the spacing of the opto-electronic elements in the CCD dictates the horizontal resolution. The characteristics of the CCD also dictate the number of discernible colours. The vertical resolution, on the other hand, depends on the stepper motor and mechanics responsible for moving the CCD down the page.

One phrase which you'll see quoted for scanners is...