flat bed scanner
Flatbed scanners are scanners for scanning two-dimensional planar originals, such as printed pages, images, photographs, etc. For this purpose, the original is placed on a glass plate, which is guided by a carriage construction over the scanning device, a line sensor.
The scanning device of a flatbed scanner consists of a fluorescent lamp that irradiates the original with a narrow white light strip. The light strip extends across the entire width of the original. The reflection of the light is bundled by mirrors, filters and lenses and detected by a line sensor, a CCD line or a CIS sensor (Contact Image Sensor), which consists of thousands of photo elements.
The charge image stored in the CCD sensor is read out one by one and fed to the D/A converter, which digitizes it. Resolution is therefore directly dependent on the number of photodiodes in the CCD sensor and can only be improved by software-based interpolation. Scanning of colors can be done by a triple line sensor with upstream color filters or by three times sequential scanning, with one scan per color.
Flatbed scanners can have optical resolutions well above 1,000 dpi and interpolated resolutions of `10^6`.