Scanners have slowly made their way into the everyday lives of the general public. They are ways in which graphical images can be inputted into the computer for touch-ups or to be distributed via the World Wide Web.
There are four types of scanners:
2. Sheet-fed Scanners: Sheet-fed scanners are similar to flatbed scanners. The only difference is that where in flatbed scanners the image you wish to scan does not move, in sheet-fed scanners the document moves, like how the piece of paper moves in a printer.
3. Handheld Scanners: These scanners operate like flatbed scanners except the user has to move the scan head (the part of a scanner responsible for scanning the image) in the place of some motorized machine. The images produced by these handheld scanners are not of very good quality.
4. Drum Scanners: Drum scanners can be used to produce very detailed graphics.
In this section, we are concentrating primarily on the flatbed scanner.
How a flatbed scanner works:
First, you place the image onto glass plate and close the cover. The top of the cover is usually white, to provide a background for your image. Then, a light source is turned on to illuminate the document on the scanner. CCD (charge-coupled device) technology is a core component of scanners. It is a device that turns light into an electric charge. CCD technology is what captures the images and allows you to convert your picture into a digital form used by your computer.
To get the image you want to scan to reach the CCD, your scanner uses a combination of prisms, lenses, and mirrors. The CCD, together with the prisms, mirrors, and lenses make up the scan head. To scan something, the scan head slowly moves across the document. As it moves along, the image is reflected by a group of mirrors onto the CCD.
After the document is scanned, it must be transferred to your computer in order for you to use it. There are several ways to do this:
SCSI is an acronym for Small Computer System Interface. It can transfer data between your scanner and computer extremely fast, but it is also extremely expensive. Usually, SCSI scanners include a special SCSI card that you insert into your computer.
Parallel ports are used by most scanners, but it is also transfers data between your scanner and computer the most slowly.
USB (universal serial bus) is not yet as popular as SCSI or parallel port, but it can transfer data fairly quickly at a pretty low cost.
Finally, you need special software that
can communicate with a scanner. Most scanners speak a common language, called
TWAIN. The software acquires the images scanned by the scanner, and then they
usually come with some sort of editing devices that allow you to make changes
to your pictures!
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