Scanning Documents in Drums and on Flatbeds

A scanner is a machine capable of reproducing an image from an original document, photo, book, art print or even three dimensional objects. They come in various styles depending on the quality of image being produced and the application for that image. Scanners are useful because they can reproduce a digital copy of anything that's possible to fit in/on the scanner being used.

It might be obviously impractical to attempt scanning something like an elephant, but the ability to scan old photographs in order to preserve them digitally makes scanners an important invention in today's digital media world.

The most familiar type of scanner for the typical consumer is the flatbed scanner. A flatbed scanner has a flat pane on which the object being scanned is placed. After pressing a button onscreen (assuming the scanner is connected to a computer) or on the scanner itself, the machine records the data produced by an array of CCD's, or charge-coupled-devices in order to produce an image.

Also, contact image sensors (CIS) can be used in flat bed scanners to produce a digital image. In both cases the CCD's and CIS's record particular bands of light, e.g. red, blue, or green and the separate color bandwidths are then recombined to make the single digital image. Like their flatbed progeny, drum scanners can also record the separate wavelengths of light to produce images.

Drum scanners utilize what is known as a photo multiplier tube in order to record the image data. Photomultiplier tubes, while technically an older technology, are actually far more effective machines for image reproduction than their flatbed cousins. As a result, drum scanners are used for high end image production, especially in media-based industries like magazines.

Another reason for their use in high-demand-for-media industries is their ability to produce images with up to 12,000 PPI, or pixels per inch. This means that images produced in a drum scanner are ideal for enlargement. Also, while film can be adequately scanned by flat bed scanners, the superior production quality of drum scanners makes them the scanners of choice when reproducing film media.

In fact, wet film can be inserted into the clear acrylic cylinder, or drum, of a drum scanner and then used to make a high quality image. Over time the monetary investment required to purchase a drum scanner has gone down, and led to additional developments in scanner technology, including document feed scanners that use machinery to automatically feed the media into the scanner to then be imaged.

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