Digital Photocopy


For those of you who still are in the posession of some old fashioned paper pictures or photo albums. The odds are that you are also a proud owner of a scanner (so am I by the way).

I’m guessing that you know what is about to happen?

Indeed! I’ll explain you how a scanner works. Isn’t that great ;-)…

Alright, off we go…

The basic priciple of a scanner is to analyze an image and to process it in some way.
This capture process allows you to save the information to a file on your computer (jpg, bmp, png, whatever).

The heart, so to speak, of a scanner is called the CCD array. The Charge-coupled device array.
Basically this is a collection of small light-sensitive diodes. These diodes convert photons (which is light) into electrons (electrical charges).
These small diodes are called “photosites”, but don’t worry about the names too much.

The technique works as followed: the brighter the light that hits the light sensitive diode (photosite) the greater the electrical charge will be.
Now, the document or picture you scan reaches this CCD array through mirrors (indeed, it’s like a magic trick), filters and lenses.

Now you know the technical details, let’s go over the scanning process.
As you probably know, you place the document or picture you like to scan on a glass plate. Before you start scanning you also close the lid.
This coves is most of the times white. Because like this it provides a uniform background that the scanner software can use as a reference to determine the size of the document that is being scanned.

Once you start scanning you’ll notive a bright light moving from one end of scanner to the other (step into the light my child!). This is used, ofcourse, to illuminate the document you are scanning.

Now during the scanning process an image of the document is reflected by an angled mirror into another mirror. In some scanners even a third mirror.
The last mirror reflects the image onto a lens and this lens focuses the image through a filter on the CCD array (the part we discussed earlier).

The scanner’s software does it’s trick and reassembles the image digitally. The image should now be transferred to the computer, this is done through a serial port, usb port, firewire port or SCSI port (or whichever ports were invented by the time you read this).

Another thing to amaze your girlfriend with!

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