hello welcome to this learner video in this video we'll be looking at flatbed scanners what they are how do they work okay so what is a flatbed scanner well it's a device that's used to digitize hard copies of documents converting a paper document into an accurate digital copy usually they work a4 to a3 size and they're more accurate than photos because when you take a photo of a document you end up with distortion because of where the lens is and also you get lighting variation as well so you don't get an accurate copy of a document when you just take a picture of it and sometimes taking a picture is okay but sometimes you need a more accurate version especially for legal documents and usually when it's digitized it's output in a form of either jpeg or pdf file and depending on the scanner that will either be sent directly to the computer or it might be emailed directly to a recipient okay so let's have a look at how they work okay so let's take a look at what happens when you scan a document so you take the document or the image and you place it face down on a glass plane that's transparent and below that glass pane are some components that enable the scanning the first component is a xenon bulb or light strip and this emits light and that light then bounces up on an angle and it hits the image as it hits the image and it gets reflected back down then the light is changed depending on the brightness of what what it hits and the color so the frequency and the intensity of the light changes and then it bounces back and as it bounces back it hits a series of mirrors and some of these mirrors are curved and their job is to direct and focus the light that's returned on a lens the job of the lens is to use light folding to concentrate the light on the surface of a ccd a charge coupled device now the ccd is made up of thousands of photo sensitive cells and the ccd bar itself all the way along here is split up into three components we've got the red the green and the blue and each of those there are just a filter across the front of the ccd cells so that it makes them more or less sensitive to different frequencies of light this means that the scanner can detect different colors as it's recording the image so the ccd takes all of these electrical signals and they're still analog signals and it sends them these signals are passed along to the next device which is the adc or the analog to digital converter the job of the analog to digital converter is to convert the raw analog signals into a stream of ones and zeros that the computer can process so that's the basic functioning of a scanner and you can see it there it starts here at the top of the pane here and the whole this whole part of it here but what's known as the scan head all of these components together move start at the end and they move all the way down scanning all the way through the document and they do that because what you have is you have two stabilizing rails here and here that hold the scan head here in place and the scan head itself moves up and down and is controlled very very precisely through the use of a stepper motor and a belt which you can see there there's the motor stepper motor and a stepper motor is a special kind of motor that is very precise and it controls the movement of this belt and that's how flatbed scanners work so just to review let's work through the steps of the scanning process so step one light is emitted from a light source usually a xenon tubule step two the light hits the image altering the intensity and frequency of the light wave and bounces back step three mirrors direct the light towards the lens which folds the light so that it can be concentrated on a charge coupled device step four the ccd cells output an analog signal which varies from each cell depending on the intensity and frequency of the light step 5 the electrical signal is passed to an analog to digital converter which converts the signal into a stream of digital data for each port of the image and then sends the data to a buffer step six a stepper motor and belt system moves the scanner head all the way along the full length of the image until the entire image is scanned and then finally step seven the data in the buffer is converted to a file such as a pdf or a jpeg and then is transferred to the computer for processing okay so that's how flatbed scanners work if you're looking for more igcc resources then pop over to learnlearn.uk i'll put a link in the description there you'll be able to find quizzes worksheets and more thank you very much