How Do Scanners Work?
Techquickie
·Techquickie
·2018-05-06
·
954 words · ~4 min read
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so it's 2:00 a.m. and you're laying alone on your coach watching reruns and
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suddenly your phone lights up with a message from a friend who needs a copy
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of a very important document that is sitting on your Cheeto dust covered
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coffee table for some reason so you go
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to take a picture of it with your phone but you realize your crappy built-in
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phone camera and the poor lighting from the dingy Bare Bulb hanging from the
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ceiling just aren't cutting it so decisively you dash to your PC and use
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your flatbed scanner and as you sit there listening to the whirling of the
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scanning mechanism and pondering how your life got to this point you find
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yourself asking how the heck do these things work
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anyways great question your typical scanner uses something called a charge
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coupled device or CCD to determine what's on the page the main idea here
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being that the CCD can convert light into an electrical charge which it then
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sends to your computer as Digital Data so when you start scanning a document
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that bright light that you see coming from inside typically from either a
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Xenon lamp or a cold cathode which as you may know is similar to what people
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used in PC case lighting a few years back hits the sheet of paper and was
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reflected back to a series of mirrors underneath the glass surface and then
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focused by a lens onto an array of CCD
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sensors since darker areas of the page containing things like text and clip art
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will reflect less light than the blank usually White areas the CCD array will
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see these differences which will show up as an accurate image of your document on
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your computer screen if you've ever had a scan of something bulky and had to
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leave the lid open a little bit you'll have noticed the scan is black in areas
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that aren't covered by anything this is because nothing's there to reflect the
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light though modern software is often smart enough to crop these areas out for
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you CCD arrays are also what determine a scanner's true resolution the more
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sensors in the array the more points of light it can capture and the more pixels
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it can send to your computer if you're in the market for a scanner make sure to
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check that the resolution on the spec sheet is the hardware resolution that
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reflects the true capabilities of the CCD array not some fake number achieved
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through software trickery like interpolation that uses average values
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of nearby pixels to approximate a higher
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pixel count image but what about color scanning this uses additional lenses and
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built-in color filters to separate the scan into red blue and green versions
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which are then processed to determine what the actual colors of your original
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document are although this is usually done with just one pass of the scanner
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some older models lack these additional lenses and so need multiple passes to
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complete a color scan which is why they were much slower in color mode but not
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every consumer level scanner works this way there are also flatbeds that use
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something called a contact image sensor or CIS instead of these ccds These are
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simpler in construction use an array of LEDs to shine light on the document so
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an image sensor can essentially take a snapshot of it like you were trying to
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do on the table with your cell phone but
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better although the scans from the CIS are typically lower quality than CCD
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scanners CIS is a cheaper more lightweight and more efficient
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technology so you'll find it in a lot of small port scanners that can be powered
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solely from a USB port instead of requiring a wall outlet of course there
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are other types of scanners out there such as expensive drum scanners with
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high dynamic range for professional applications as well as 3D scanners
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which you can learn more about right up here but hopefully this episode has
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given you a little insight into how your scanner at home works and let us know
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down in the comments down below if you'd like to see a future episode on what
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something hilarious over there they usually are and I'm going to roll out
5:00
like a drum scanner