so it's 2:00 a.m. and you're laying alone on your coach watching reruns and
suddenly your phone lights up with a message from a friend who needs a copy
of a very important document that is sitting on your Cheeto dust covered
coffee table for some reason so you go
to take a picture of it with your phone but you realize your crappy built-in
phone camera and the poor lighting from the dingy Bare Bulb hanging from the
ceiling just aren't cutting it so decisively you dash to your PC and use
your flatbed scanner and as you sit there listening to the whirling of the
scanning mechanism and pondering how your life got to this point you find
yourself asking how the heck do these things work
anyways great question your typical scanner uses something called a charge
coupled device or CCD to determine what's on the page the main idea here
being that the CCD can convert light into an electrical charge which it then
sends to your computer as Digital Data so when you start scanning a document
that bright light that you see coming from inside typically from either a
Xenon lamp or a cold cathode which as you may know is similar to what people
used in PC case lighting a few years back hits the sheet of paper and was
reflected back to a series of mirrors underneath the glass surface and then
focused by a lens onto an array of CCD
sensors since darker areas of the page containing things like text and clip art
will reflect less light than the blank usually White areas the CCD array will
see these differences which will show up as an accurate image of your document on
your computer screen if you've ever had a scan of something bulky and had to
leave the lid open a little bit you'll have noticed the scan is black in areas
that aren't covered by anything this is because nothing's there to reflect the
light though modern software is often smart enough to crop these areas out for
you CCD arrays are also what determine a scanner's true resolution the more
sensors in the array the more points of light it can capture and the more pixels
it can send to your computer if you're in the market for a scanner make sure to
check that the resolution on the spec sheet is the hardware resolution that
reflects the true capabilities of the CCD array not some fake number achieved
through software trickery like interpolation that uses average values
of nearby pixels to approximate a higher
pixel count image but what about color scanning this uses additional lenses and
built-in color filters to separate the scan into red blue and green versions
which are then processed to determine what the actual colors of your original
document are although this is usually done with just one pass of the scanner
some older models lack these additional lenses and so need multiple passes to
complete a color scan which is why they were much slower in color mode but not
every consumer level scanner works this way there are also flatbeds that use
something called a contact image sensor or CIS instead of these ccds These are
simpler in construction use an array of LEDs to shine light on the document so
an image sensor can essentially take a snapshot of it like you were trying to
do on the table with your cell phone but
better although the scans from the CIS are typically lower quality than CCD
scanners CIS is a cheaper more lightweight and more efficient
technology so you'll find it in a lot of small port scanners that can be powered
solely from a USB port instead of requiring a wall outlet of course there
are other types of scanners out there such as expensive drum scanners with
high dynamic range for professional applications as well as 3D scanners
which you can learn more about right up here but hopefully this episode has
given you a little insight into how your scanner at home works and let us know
down in the comments down below if you'd like to see a future episode on what
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like a drum scanner