Scanners and touchscreens
Posted in Computing, HardwareScanners
Scanners work by passing a scanner head across the image placed in the scanner. The scan head moves across the image from one side to the other shining a bright light. The scan head measures the intensity of light reflected by each area of the image. The scanner converts this analogue signal to digital storing the data in memory. For a black and white scan only 1 bit is needed for each area. The more bits the more shades of grey can be used with 1 byte per area leading to 256 different shades of grey.
Resolution describes how small of an area the image is split up into and is measured in Dots Per Inch (DPI) the more dots per inch the higher the quality of the scanned image however the more memory it will consume.
Colour scanners
Colour scans can be made by passing the scan head over the image 3 different times. Each time a different filter is used so only red, blue and green light is used and reflected. The 3 different images are then combined to form one single colour scan.
Touch screens
On a touch screen input system data is entered and commands are executed by touching or pressing a specific area on a screen. Touch screens allow tasks to be quickly carried out by the user, such as at a till in a supermarket or fast food restaurant.
Some touch screens respond to pressure on the screen whilst others use a capacitive overlay where by a layer is put over the screen which is lined with a conducted coating. The screen is triggered by finger pressure which causes electrical contact at the point of touch.