Scanners

= = by** **Mornay**
 * Scanners

They say a picture is worth a thousand words. What that really means is that pictures contain a huge amount of information. To describe a complex picture, you might need far more than a thousand words! Now just imagine if you're a computer and you want to make sense of a picture like the Mona Lisa. Where do you begin? People find this job easy because a huge part of our brain (something like 25 percent) is devoted to processing the things we can see with our eyes. But if you're a computer, you can't process a whole picture at once like a person can; instead, you have to go about trying to understand the information the picture contains in a much more systematic way.



A scanners job is to turn a picture a human can understand into a digital picture that a computer can store and process an image coded in the form of millions of numbers (zeros and ones) called B inary Code. A scanner does this by moving a scaning head backwards and forwards across the picture to recreate the image, one line at a time, inside the computer. This process is called scanning and that's how a scanner gets its name.



There are several different types of scanner, but they all work in broadly the same way. The most popular ones are flat-bed scanners, which look a bit like photocopiers that have been on a diet. You open up a lid, place the document you want to scan face down on a piece of glass, and then close the lid again. When you tell the computer to scan, the scanner moves its scanning head from side to side and progessively down the page until it's covered the entire printed area. It detects the pattern of light being reflected into it off the printed page and produces a series of electrical signals. This effectively converts the light pattern on the page into a pattern of numbers that your computer can store.



Once you've scanned a page, you end up with an image file on your computer. If you've scanned a page from a book, what you have is effectively a photograph of a page from a book. You still don't have the words in your computer in a form that you can paste into a word-processor and edit.To do this you need OCR software. Indeed, your computer doesn't even know that the image you scanned is a page: for all it knows you might have scanned a photograph. Some people have even been known to scan their own faces!