If you work with hard copy documents, you're going to need a document scanner a lot. Document scanners are of three types-flatbed, hand-held and sheet-fed. Of these, flatbed scanners work in a way that requires users to place the scannable document on the glass pane inside the device. Within the flatbed scanner lies an image sensor which moves down the page and copies its contents.
Hand-held scanners are used manually by the user. Here, the user must manually move the sensor over the length of the document so that it is scanned.
Pressure Canner
A sheet-fed scanner is just like a printer in the sense that it glides the sheet of paper over the sensor to get a scanned image of the page.
The CCD Sensor: Usually, scanners use a charge-coupled device (CCD) or a Contact Image Sensor (CIS) for its image sensor. However, drum scanners work with a photomultiplier tube as its image sensor. The image sensor of most document scanners comprises a range of charge-coupled devices. This refers to the device responsible for the movement of electrical charge from inside the device to a situation where it can be manipulated or converted into digital values.
This CCD range works through photo-sensitive diodes that convert light they catch into an electric signal carrying the same data. In flatbed scanners, the CCD array has a light within the scanner that brightens up the page and makes it easier for the array to read. Usually, sensors work in a three color mode - RGB. This means that the document's image will be separated into these three images - red, green and blue - by a lens before they are replaced when they can be seen on a computer.
The CIS Sensor: Here, the contact image sensor is different. It contains hundreds of RGB LED lights. When in combination, they become white light. To scan a document, the sensor is placed really close to the document with a glass pane separating them. When the document is scanned, it throws up white light. At this point, sensors pick up the image of the document.
Transfer to the computer: The scanning process ends with the scanned image being transferred to the attached computer. A document scanner can be attached to a computer by way of a USB, Small Computer System Interface, a group of computers connected to a common scanner or by FireWire. The language scanners understand and read is called TWAIN. These language drivers are usually accompanied by programs like PhotoShop and form part of the installation CD which comes with the scanner you buy.
Once the image is available on the computer, it can be put into different file types such as PDF for document viewing, or PNG which shows an uncompressed image with very high quality but which uses a lot of memory space, and JPG, another file compression tool that reduces the size of image files and consequently its image quality.
So, if you need a document scanner, choose wisely from the above types and ensure that you get the most out of it.
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Oct 31, 2011 15:07:46
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