how does a scanner work
Types of scanners
Scanners are devices that allow you to input documents and pictures that you have hard copies off. The scanned documents can be saved to a file, and then you can edit them in Photoshop if its an image, or you can edit them in Microsoft word or another word processor.
Scanners are used primarily by home users, but these are the desktop type scanners. There are also large full page,and multi page scanners used by the printing industry, and especially the engineering industry. Scanners are widely used in the printing and publishing industry and even at home due to increased popularity of multi function printers.
Flatbed scanners are the most widely sold and used of all the types of scanners. These use a flat glass platform where your document is placed face down on the glass surface. There is then a small motor that move the lamp over the document.
A handheld scanner will scan the image using the same method as a flatbed scanner, the difference is that when you scan the document you have to actually roll the scanner device over the paper and keep the paper flat, and stationary. These types of scanners can be large A4 handheld scanners, and they can also be just single pen sized handheld scanners that will scan a document one line at a time.
Sheet fed scanners are mostly found in home printers, and also in larger printer combinations which also combine photocopiers. This are typically found in large offices though, and will be too large for the average home user. If you have lots of paper that you need scanned, then the type of scanner that doubles as a flatbed scanner as well as an ADF function. This stands for automatic document feeder. This means your scanner will be able to scan in around 30-50 documents at a time. The price range for this type of scanner is within the budget of small business users, or home users.
Drum scanners are very high end and expensive scanners that are used in the printing and publishing industry to help them produce high-quality graphic images. The image that needs to be scanned is usually a very high quality image, and it is placed on a glass drum or cylinder. The scanner uses a PhotoMultiplier Tube (PMT) which converts the optical signals reflected directly from the image into an electrical signal
Glass plate and scanner cover
The glass plate functions as a platform where the user can place the document In the scanner, the glass plate is made of acrylic, and the scanner surface will be white, to help reflect the light.
Scanning head assembly
The scanning head is what contains a light source, and also a set of mirrors, and a lens that focuses the light into a charged coupled device. The light source is made from a Cold Cathode Fluorescent Lamp (CCFL), which is used to illuminate the main document surface. An array of charged-coupled devices (CCDs) or a Contact Image Sensor (CIS) converts the optical signals into electrical signals.
Stepper motor assembly
The stepper motor assembly is used to precisely move the scanning head across the surface of the document. The scanning head is attached to the stepper motor using a belt mechanism.
The device driver acts as an interface between the scanner and also the operating system.
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