<P> Color scanners typically read RGB (red - green - blue color) data from the array . This data is then processed with some proprietary algorithm to correct for different exposure conditions, and sent to the computer via the device's input / output interface (usually USB, previous to which was SCSI or bidirectional parallel port in older units). </P> <P> Color depth varies depending on the scanning array characteristics, but is usually at least 24 bits . High quality models have 36 - 48 bits of color depth . </P> <P> Another qualifying parameter for a scanner is its resolution, measured in pixels per inch (ppi), sometimes more accurately referred to as Samples per inch (spi). Instead of using the scanner's true optical resolution, the only meaningful parameter, manufacturers like to refer to the interpolated resolution, which is much higher thanks to software interpolation . As of 2009, a high - end flatbed scanner can scan up to 5400 ppi and drum scanners have an optical resolution of between 3,000 and 24,000 ppi . </P> <P> "Effective resolution" is the true resolution of a scanner, and is determined by using a resolution test chart . The effective resolution of most all consumer flatbed scanners is considerably lower than the manufactures' given optical resolution . Example is the Epson V750 Pro with an optical resolution given by manufacturer as being 4800dpi and 6400dpi (dual lens), but tested "According to this we get a resolution of only about 2300 dpi - that's just 40% of the claimed resolution!" Dynamic range is claimed to be 4.0 Dmax, but "Regarding the density range of the Epson Perfection V750 Pro, which is indicated as 4.0, one must say that here it doesn't reach the high - quality (of) film scanners either ." </P>

An optical scanner is a device in the _ _ component of a computer system